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R.
H
OUART
&
V.
H
ÉROS
N
OVAPEX
20(1-2): 1-12, 10 juin 2019
1
The genus Gemixystus Iredale, 1929 (Gastropoda: Muricidae: Trophoninae)
in New Caledonia with the description of two new species and some notes
on the genus in the Indo-West Pacific
Roland HOUART
Research associate
Institut royal des Sciences naturelles de Belgique, rue Vautier, 29, 1000 Bruxelles
and
Institut Systématique Evolution Biodiversité (UMR7205 ISyEB), Muséum national d'Histoire
naturelle, CNRS, Sorbonne Université, EPHE, 57 rue Cuvier, CP 26, 75005 Paris, France.
roland.houart@skynet.be
Virginie HÉROS
Institut Systématique Evolution Biodiversité (UMR7205 ISyEB), Muséum national d'Histoire
naturelle, CNRS, Sorbonne Université, EPHE, 57 rue Cuvier, CP 26, 75005 Paris, France.
malaco@mnhn.fr
Keywords. Gastropoda, Muricidae, Trophoninae, Gemixystus, New Caledonia, new species.
ABSTRACT. The genus Gemixystus Iredale, 1929 in New Caledonia is reviewed. Five species are
recorded of which two are new, G. impolitus n. sp. and G. lenis n. sp. Gemixystus stimuleus
(Hedley, 1912) is recorded for the first time in New Caledonia. Gemixystus transkeiensis (Houart,
1987) is re-transferred from Vaughtia to Gemixystus. The 12 extant species of Gemixystus are
illustrated.
INTRODUCTION
The genus Gemixystus in Australia and New Zealand was reviewed by Houart (2004) who included
eight extant and six fossil species in this genus, of which G. polyphyllius (Tenison-Woods, 1879) is
known from both extant and fossil specimens. A ninth extant species was described by Houart &
Héros (2012) from the Chesterfield Reefs.
To date, molecular data of Gemixystus has not been analysed. In Barco et al. (2012) it was
considered incertae sedis. We here provisionally retain Gemixystus in Trophoninae, pending future
genetic analyses.
With the present revised classification, the new species described in 2012, and the two new ones
described here, twelve extant species are currently assigned to Gemixystus: G. calcareus Houart &
Héros, 2012, Coral Sea, Chesterfield Reefs; G. fimbriatus Houart, 2004, New South Wales, South
Australia and Tasmania (Fig. 6A-B); G. impolitus n. sp., Chesterfield Reefs; G. laminatus (Petterd,
1884), South Queensland, Australia to Tasmania; G. lenis n. sp., Chesterfield Reefs; G. leptos
(Houart, 1995), South Queensland, Australia and Chesterfield Reefs; G. polyphillius (Tenison-
Woods, 1879), extant: New South Wales, Australia and S Tasmania; fossil: Miocene, Victoria
(Fig. 6G-H); G. recurvatus (Verco, 1909), New South Wales, Australia and South Australia (Fig.
6I-J); G. rhodanos Houart, 2004, South Queensland, Australia to Tasmania (Fig. 6K-L); G.
rippingalei (Houart, 1998), Queensland, Australia; G. stimuleus (Hedley, 1908), South Queensland
and New South Wales, Australia; G. trankeiensis (Houart, 1987), Transkei, South Africa (Fig. 6N-
P).
Adult shells of Gemixystus are small, rarely exceeding 7 mm in length. The largest being G.
laminatus and G. recurvatus and the smallest G. stimuleus, the latter not exceeding 3.5 mm in
length.
Material and methods
Material
The material studied here primarily includes
specimens collected on various cruises conducted by
the MNHN/IRD in New Caledonia. Other illustrated
specimens are from the collections of the Australian
Museum, Sydney, the KwaZulu-Natal Museum, South
Africa, the South Australian Museum, Adelaide, the
Tasmanian Museum, Hobart, and the personal
collection of the first author.
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OUART
&
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ÉROS
The genus Gemixystus in New Caledonia
2
Specimens from the following expeditions of the
MNHN/IRD were examined:
SMIB 8 (1993) DOI
10.17600/93000640 ; BATHUS 2 (1993) DOI 10.17600/93000360;
BATHUS 3 (1993) DOI 10.17600/93000370; BATHUS 4 (1994)
DOI 10.17600/94100030; NORFOLK 1 (2001) DOI
10.17600/1100050; EBISCO (2005) DOI 10.17600/5100080;
KANACONO (2016) DOI 10.17600/16003900 ; KANADEEP
(2017) DOI 10.17600/17003800.
These missions were aimed at exploring the seabed
around New Caledonia and continuing the exploration
in the Coral Sea with the Chesterfield Plateau and
Bellona Reefs, as well as the Lansdowne-Fairway
Reefs.
Morphological analyses
The characters used to describe shell morphology
address the general aspect of the shell, its shape, size,
and colour, the shape of the spire including the
number and features of the protoconch and teleoconch
whorls, details of the suture and of the subsutural
ramp, details of axial and spiral sculpture, the
aperture, the siphonal canal, and when available, the
characters of the operculum and radula.
The method used to determine diameter and height,
and to count the number of protoconch whorls,
follows Bouchet & Kantor (2004) as shown in Fig. 1.
The bathymetric ranges given herein are the inner
values of the recorded depths: the deepest minimum
and the shallowest maximum of each recorded depth
range.
Figure 1. Method for determining diameter, height and counting the number of protoconch whorls.
ABBREVIATIONS
Repository
AMS: The Australian Museum, Sydney, Australia.
MNHN: Muséum national d'Histoire naturelle, Paris,
France.
NM: KwaZulu-Natal Museum, Pietermaritzburg,
South Africa.
RH: collection of Roland Houart.
SAMA: South Australian Museum, Adelaide, South
Australia.
TAM: Tasmanian Museum.
Other
IRD: Institut de Recherche pour le Développement.
Station number prefixes
CP: Chalut à perche (beam trawl).
DW: Drague Warén (Warén dredge).
Specimens
dd: empty shell(s).
lv: live collected specimen(s).
Terminology used to describe the spiral cords and
the apertural denticles (after Merle 2001, 2005)
(Fig. 3A-F). Variable features are given in
parentheses.
Convex part of teleoconch whorl and siphonal canal
ab: abapical (or abapertural);
ABP: abapertural primary cord on the siphonal canal;
ad: adapical (or adapertural);
ADP: adapertural primary cord on the siphonal canal;
MP: median primary cord on the siphonal canal;
P: primary cord;
P1: shoulder cord;
P2-P5: primary cords of the convex part of the
teleoconch whorl;
s: secondary cord;
s1-s2: secondary cords of the convex part of the
teleoconch whorl (s1 = secondary cord between P1
and P2; s2 = secondary cord between P2 and P3).
Aperture
D1 to D5: abapical denticles.
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20(1-2): 1-12, 10 juin 2019
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Figure 2. Radula of Gemixystus leptos. Holotype MNHN-IM-2000-970 (scale bar 10 µm).
SYSTEMATICS
Family MURICIDAE Rafinesque, 1815
Subfamily TROPHONINAE Cossmann, 1903
Genus Gemixystus Iredale, 1929
Type species by original designation: Trophon
laminatus Petterd, 1884, Recent, southeastern
Australia (Fig. 6C-F).
Apixystus Iredale, 1929. Type species by original
designation: Trophon stimuleus Hedley, 1907, Recent,
eastern Australia (Fig. 5K-T).
Remarks. Iredale (1929: 185) separated Gemixystus
from Apixystus because of their different protoconch
morphology, Gemixystus having an “angulate apex”
(Fig. 6F) compared to the “smooth rounded apex” of
Apixystus (Fig. 5S-T). However, such differences in
Muricidae are now considered to be a useful tool at
the specific level only. The two taxa were recognized
as congeneric by Houart (2004).
He also transferred two South African species
formerly described in Apixystus Iredale, 1929, a
synonym of Gemixystus, to other genera and
subfamilies. Apixystus kilburni Houart, 1987 was
transferred to Pazinotus Vokes, 1970 (Muricopsinae)
and A. transkeiensis Houart, 1987 to Vaughtia Houart,
1995 (Ocenebrinae). This new classification was taken
over by Houart et al. (2010).
The classification of A. kilburni in Pazinotus is not
questioned, but A. transkeiensis is here reintroduced to
Gemixystus after a re-examination of the material. The
small, light shell of G. transkeiensis with a broad last
teleoconch whorl strongly constricted at base, a broad
aperture and an expanded apertural varix; a long,
open, siphonal canal and a spiral sculpture consisting
of 9-11 axial lamellae on the last teleoconch whorl,
together with the broad, broadly open spinelets at
intersection of the axial lamellae and the five rounded,
spiral cords have prompted us to review its
classification.
Gemixystus calcareus Houart & Héros, 2012
Figs 3A; 4A-B
Gemixystus calcareus Houart & Héros, 2012: 30, fig.
2C, D, N
Type locality. Coral Sea, Chesterfield Reefs, 19°36’S,
158°43’E, 568-570 m [EBISCO: stn DW2603].
Type material. Holotype (dd) MNHN-IM-2000-
24180.
Other material examined. New Caledonia, Coral
Sea, Chesterfield Reefs, EBISCO, stn DW2603,
19°36'S, 158°43'E, 568-570 m, 4 dd, MNHN-IM-
2012-41629, 1 dd, RH.
Distribution. Only known from empty shells from the
type locality.
Original description. Shell medium-sized for the
genus, height 5.4 mm, height/width ratio 1.7. Broadly-
ovate, lightly built, lamellate. Subsutural ramp narrow,
weakly sloping, weakly convex. Shell entirely chalk-
white. Spire high with 1.6 protoconch whorls and 4.2
broad, weakly shouldered teleoconch whorls. Suture
of teleoconch whorls impressed, partially obscured by
small axial lamellae of following whorl. Protoconch
comparatively large, broad, weakly acuminate with
broad keel adapically, otherwise smooth. Diameter
500 μm. Terminal lip delicate, thin, weakly curved.
Axial sculpture of teleoconch whorls consisting of
low, narrow, frilled lamellae, each with short, broad,
open spinelets occurring at crossings of axial lamellae
with spiral cords. Spines more conspicuous on P1.
First whorl with 8 lamellae, 2nd with 13, 3rd with 16
and 4th with 20. Apertural lamella strongly erect,
broad. Spiral sculpture of low, broad, rounded primary
cords: P1-P3 visible on 1st to 3rd whorl with slightly
visible, very narrow P2. P3 partially covered by
following whorl. Last teleoconch whorl with P1-P5,
ADP, MP. P1-P5 equidistant, P1 slightly larger, P2
narrow. ADP and MP narrower, MP low.
Aperture broad, rounded. Columellar lip narrow,
smooth. Lip adherent at adapical extremity. Anal
notch obsolete. Outer lip strongly erect with five
weak, elongate denticles within: D1-D5. D4 and D5
narrower, more strongly elongate within. Siphonal
canal short, narrow, straight, open, with ADP and MP
and low axial lamellae over whole length.
R.
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OUART
&
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ÉROS
The genus Gemixystus in New Caledonia
4
Remarks. Gemixystus calcareus differs from G.
stimuleus in having a comparatively larger shell with
twice as large protoconch, more numerous axial
lamellae, 20 vs 11 or 12 on last whorl and 16 vs 13-15
on penultimate whorl. The spiral sculpture also
differs, G. calcareus having P1-P5, ADP and MP on
the last teleoconch whorl vs P1-P3 in G. stimuleus,
without any spiral sculpture on the siphonal canal.
Gemixystus calcareus also differs from G. rippingalei
(Figs 3E, 6M) from Queensland, Australia, in having a
comparatively larger shell, G. rippingalei reaching
only 4.4 mm in length and having a longer siphonal
canal; also in having a less spiny shell and different
spiral sculpture morphology. G. rippingalei having a
last whorl with closely spaced P1-P4.
Gemixystus impolitus n. sp.
Figs 3B; 4C-H
Material examined. New Caledonia, Coral Sea,
Lord Howe Rise, Banc Capel, KANADEEP, stn
CP4934, 25°04'S, 159°55'E, 290-300 m, 1 dd,
holotype MNHN-IM-2000-34501; Banc Kelso, stn
DW4949, 24°07'S, 159°41'E, 280-300 m, 1 dd,
paratype MNHN-IM-2000-34502; Banc Nova, stn
DW5011, 22°07'S, 159°19'E, 340-550 m, 1 dd,
paratype MNHN-IM-2000-34503
Other material examined. Coral Sea, South
Landsdowne, EBISCO stn DW2629, 21°06'S,
160°46'E, 569-583 m, 1 dd.
Type locality. Coral Sea, Lord Howe Rise, Banc
Capel, 25°04'S, 159°55'E, 290-300 m.
Distribution. Lord Howe Rise: Bancs Capel, Kelso
and Nova and South Landsdowne, empty shells at
300-569 m.
Description of the holotype. Shell small, 4 mm in
length. Length/width ratio 1.7. Biconical, broadly
ovate. Heavy, weakly spinose, squamous, angulate.
Subsutural ramp broad, strongly sloping, weakly
convex.
Ivory white to light tan with darker coloured
subsutural area. Aperture white.
Spire high with 1.5 protoconch whorls. Teleoconch of
3.5 broad, angulate, strongly shouldered, weakly
spinose whorls. Suture of whorls impressed.
Protoconch large, broad. Whorls rounded, smooth.
Maximum width 400 µm, height 500 µm. Terminal lip
shallow, thin, weakly opisthocline.
Axial sculpture of teleoconch whorls consisting of
moderately high, narrow, nodose, weakly spinose
varices; each varix with nodes and small, open
spinelets. Other axial sculpture of numerous, low,
narrow growth lamellae. Seven varices on first and
second whorls, 5 on last. Spiral sculpture of low,
rounded, narrow, squamous primary and secondary
cords, with weakly broader P1 and P2, followed
abapically by lower P3-P5 and ADP. Low s1
secondary cord between P1 and P2, and s2 between P2
and P3. Crossing of P1 and P2 with axial varices
giving rise to short, open, acute spinelets, less
conspicuous on apertural varix. P3-P5 weakly nodose
on varices.
Aperture moderately large, roundly ovate. Columellar
lip narrow, with 2 weak, small knobs abapically; rim
broken. Anal notch very broad, shallow. Outer lip
narrow, weakly erect, with weak, narrow, elongate D3
and D4; D1 and D2 obsolete. Siphonal canal short,
narrow, slightly dorsally recurved, open.
Operculum and radula unknown.
Remarks. This new species is somewhat atypical for
the genus, in having broader varices instead of axial
lamellate varices as in the other species. However it is
here included in Gemixystus because of its biconical
small shell with a broadly ovate aperture with typical,
narrow, elongate denticles within the outer lip. These
denticles are mostly situated at adapical part of the
aperture, with a strong, elongate D4 and absent ID and
D1. The shell also has a typical, broad, expanded,
apertural varix and a broadly open, short, siphonal
canal.
Figure 3. Spiral sculpture and apertural denticles morphology
A. Gemixystus calcareus Houart & Héros, 2012. Chesterfield Plateau, 19°36' S, 158°43' E, 568-570 m, RH, 4.9
mm.
B. Gemixystus impolitus n. sp. KANADEEP, stn CP4934, 25°04'S, 159°55'E, 290-300 m, holotype MNHN-IM-
2000-34501, 4 mm.
C-D. Gemixystus leptos (Houart, 1995). C. Coral Sea, 19°40' S, 158°27' E, 245-252 m, holotype MNHN-IM-
2000-970, 4.8 mm; D. KANACONO, stn DW4695, North Iles des Pins, 22°47' S, 167°27' E, 200-290 m,
MNHN, 5.1 mm.
E. Gemixystus rippingalei Houart, 2004. Australia, Queensland, E of Lady Musgrave Island, 23°62.5'-23°51.9'
S, 152°427'-152°41.7' E, 296 m, holotype AMS C.313232, 4 mm (photo Alison Miller, AMS).
F. Gemisxystus stimuleus (Hedley, 1908). New South Wales, Sydney, 22 miles east of Narraben, 146 m,
holotype AMS C.25787, 3.0 mm (photo Alison Miller, AMS).
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H
OUART
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V.
H
ÉROS
The genus Gemixystus in New Caledonia
6
A paratype of 4.8 mm, also with 3.5 teleoconch
whorls (Fig. 4E-F) is entirely light brown coloured. It
has three denticles within the outer apertural lip (D2-
D4) with obsolete D1, a broader protoconch of 600
µm high and wide. The spiral and axial sculpture as
well as the apertural denticles are more conspicuous
but otherwise are similar to the holotype.
Gemixystus stimuleus (Fig. 5K-T) differs by its lighter
shell with narrow, more numerous lamellae, by the
absence of any other axial sculpture, by the three
spiral cords on the last teleoconch whorl instead of
five in G. impolitus n. sp. and in having a narrower
and smooth siphonal canal.
Etymology. Impolitus (L), unpolished, rough, named
for the rough appearance of the shell.
Gemixystus lenis n. sp.
Fig. 4I-N
Material examined. New Caledonia, Coral Sea,
Lord Howe Rise, Banc Argo, KANADEEP, stn
DW4956, 23°13'S, 159°35'E, 295 m, 1 dd, holotype
MNHN-IM-2000-34504; Banc Kelso, stn DW4951,
24°12'S, 159°41'E, 270-385 m, 1 lv, 1 dd, paratypes
MNHN-IM-2000-34505 (syntopic with G. leptos).
Type locality. Coral Sea, Lord Howe Rise: Banc
Argo, 23°13'S, 159°35'E, empty shells at 295 m.
Distribution. Coral Sea: Bancs Argo and Kelso,
living at 270 m.
Description of the holotype. Shell very small, 2.9
mm in length. Length/width ratio 1.6. Biconical,
broad, smooth, lightly built. Subsutural band narrow,
weakly sloping, weakly convex.
Shell entirely white.
Spire high with 1.75 protoconch whorls and
teleoconch consisting of 3 broad, weakly convex,
weakly shouldered whorls. Suture of whorls
impressed. Protoconch large, weakly elongate, whorls
longitudinally keeled, otherwise smooth. Maximum
width 450 µm, height 500 µm. Terminal lip low,
delicate, thin, weakly prosocline.
Axial sculpture of teleoconch whorls consisting of
low, weak, narrow lamellae. Apertural lamellae broad,
flaring. First and second whorls with 7 lamellae, last
whorl has 6 with a broad space between penultimate
and last lamellae. No trace of spiral sculpture except
low P1 giving rise to small, broad, low, open spines at
intersection with axial lamellae.
Aperture large, broad, roundly ovate. Columellar lip
broad, smooth, rim weakly erect, a small portion
adherent at adapical extremity. Anal notch shallow,
very broad. Outer lip narrow, weakly erect, with 4
strong, elongate denticles within, consisting of D1-D4
with D1 highest and broadest. Siphonal canal short,
narrow, weakly dorsally recurved, broadly open.
Operculum and radula unknown.
Remarks. The holotype is subadult and both
paratypes are also juveniles of 2.1 and 2.3 mm in
length, consisting of two teleoconch whorls and
featuring all the characteristics of the holotype.
Gemixystus lenis n. sp. differs from all the other
Gemixystus species in lacking any spiral sculpture
except a low P1 cord and in having a wide distance
between the penultimate and the last varix.
Etymology. Lenis (L), smooth, soft, named for the
smooth shell.
Gemixystus leptos Houart, 1995
Figs 3C-D; 5A-J
Apixystus leptos Houart, 1995: 490, figs 28-29, 86-
89,134-136.
Apixystus leptos ― Houart, 1998: 100, figs 18-19.
Gemixystus leptos ― Houart, 2004: 6, figs 5-7, 9-11,
22, 30-32, 37.
Gemixystus leptos ― Houart & Héros, 2012: 31, fig.
2G.
Type locality. Coral Sea, Chesterfield Plateau,
19°40'S, 158°27'E, 245-252 m, lv [MUSORSTOM 5:
stn DW346]
Figure 4. Scale bars 250 µm.
A-B. Gemixystus calcareus Houart & Héros, 2012. Coral Sea, Chesterfield Reefs, 19°36’S, 158°43’E, 568-
570 m, holotype MNHN-IM-2000-24180, 5.4 mm.
C-H. Gemixystus impolitus n. sp. C-D, H. KANADEEP, stn CP4934, 25°04'S, 159°55'E, 290-300 m, holotype
MNHN-IM-2000-34501, 4 mm; H. Protoconch; E-F. KANADEEP, stn DW5011, Banc Nova, 22°07' S, 159°19'
E, 340-550 m, paratype MNHN-IM-2000-34503, 4.8 mm.
I-N. Gemixystus lenis n. sp. I-K, M-N. KANADEEP, stn CP4956, 23°13' S, 159°35' E, Banc Argo, 295 m,
holotype MNHN-IM-2000-34504, 2.9 mm; M-N. Protoconch; L. KANADEEP, stn DW4951, Banc Kelso,
24°12' S, 159°41' E, 270-385 m, paratype MNHN-IM-2000-34505, 2.2 mm.
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The genus Gemixystus in New Caledonia
8
Type material. Holotype MNHN-IM-2000-970.
Other material examined. New Caledonia. Coral
Sea, between Chesterfield and Bellona Reefs,
EBISCO, stn DW2574, 20°20'S, 158°45'E, 358-374
m, 2 dd; Lansdowne-Fairway Reefs: stn DW2617,
20°06'S, 160°22'E, 427-505 m, MNHN-IM-2017-256,
1 lv; stn DW2632, 21°05' S, 160°45' E, 297-378 m, 13
dd.
Banc Kelso, KANADEEP, stn DW4951, 24°12'S,
159°41'E, 270-385 m, 1 dd (syntopic with G. lenis n.
sp.); stn DW4954, 24°12'S, 159°41'E, 300 m, 1 dd.
North of New Caledonia, Grand Passage, BATHUS
4, stn DW918, 18°49'S, 163°16'E, 613-647 m,
MNHN-IM-2012-33083, 1 dd.
Norfolk Ridge, South of New Caledonia, SMIB 8,
stn DW166, 23°38'S, 167°43'E, 433-450 m, MNHN-
IM-2012-33088, 1 dd; stn DW167, 23°38'S, 167°43'E,
430-452 m, MNHN-IM-2012-33007, 1 lv; stn
DW169, 23°37'S, 167°42'E, 447-450 m, MNHN-IM-
2012-33086, 2 lv; stn DW 170-172, 23°41'S, 168°00'-
168°01'E, 230-290 m, 1 dd; stn DW182-184, 23°18'-
23°19'S, 168°05'E, 305-367 m, MNHN-IM-2012-
32982, 2 lv, 4 dd; stn DW190, 23°18'S, 168°05'E,
305-310 m, MNHN-IM-2012-32983, 4 dd.
BATHUS 2, stn DW714, 22°38'S, 167°10'E, 124 m,
MNHN-IM-2017-362, 3 dd;, MNHN-IM-2014-2453,
1 dd; stn DW715, 22°39'S, 167°11'E, 202-227 m,
MNHN-IM-2012-33085, 1 dd; stn DW724, 22°48'S,
167°26'E, 344-358 m, MNHN-IM-2010-4899, 1 dd;
BATHUS 3, stn CP805, Banc Jumeau Ouest, 23°41'S,
168°01'E, 278-310 m, MNHN-IM-2012-32986, 1 lv;
stn DW809, Banc Jumeau Ouest, 23°39'S, 167°59'E,
650-730 m, MNHN-IM-2012-32984, 2 dd; stn
DW824, Nord Banc Antigonia 23°19'S, 168°00'E,
601-608 m, MNHN-IM-2012-32985, 2 dd; stn
DW829, Nord Banc Antigonia , 23°21'S, 168°02'E,
386-390 m, MNHN-IM-2012-33084, 1 dd.
NORFOLK 1, stn DW1722, Banc Antigonia, 23°16'S,
168°01'E, 540-540 m, MNHN-IM-2012-9285, 1 dd;
stn DW1723, Banc Crypthelia, 23°18'S, 168°15'E,
267-266 m, MNHN-IM-2012-9246, 2 dd.
NORFOLK 2, stn DW2040, Banc Jumeau Ouest,
23°41'S, 168°01'E, 285 m, MNHN-IM-2012-9298, 2
dd.
KANACONO, stn DW4677, 22°53'S, 167°35'E, 376-
390 m, 1 dd; stn DW4685, 22°28'S, 167°29'E, 404-
405 m, 1 dd; stn DW4686, 22°29'S, 167°31'E, 249-
255 m, 1 dd; stn DW4695, 22°47'S, 167°27'E, 200-
290 m, 1 dd.
Distribution. South Queensland, Australia to the
Coral Sea and the Norfolk Ridge. Only recorded dead
in Australia, from 31-73 m; New Caledonia, recorded
alive in 124-447 m.
Original description. Shell up to 4.9 mm in length
(AMS C150077), spinose, delicate. Spire high with
1.75 protoconch whorls and up to 5 angulate,
shouldered, spinose teleoconch whorls. Protoconch
acuminate, rounded or keeled, whorls smooth, glossy;
terminal varix erect, delicate, thin. Suture impressed.
Axial sculpture consisting of sharp, erect lamellae.
First whorl with 10 or 11 lamellae, second and third
whorls with 11 lamellae, last whorl with 10 or 11
lamellae. Spiral sculpture consisting of weak, rounded
cords. First to fourth teleoconch whorls with visible,
broadly spaced P1 and P2; last whorl with broadly
spaced P1 and P2, followed abapically by narrow,
closely spaced, low P3 and P4. Last whorl of a few
specimens with s1 between P1 and P2 (AMS
C.321889). Short to moderately long, narrow, open
spinelets occurring at crossing of axial and spiral
sculpture. Spine on P1 longest.
Anal notch obsolete. Outer apertural lip smooth, with
5 strong, narrow, strongly elongate denticles within:
D1 (split), D2, D3 (split). Siphonal canal short, 9-
11% of total shell length, narrow, weakly abaxially
bent, open, smooth. Translucent milky white with
traces of pale brown on last teleoconch whorl.
Rachidian radular tooth with long central and
marginal cusps and short lateral denticles. Lateral
teeth sickle-shaped. Aperture rounded. Columellar lip
flaring, smooth, partially erect, weakly adherent at
adapical extremity.
Figure 5. Scale bars 250 µm
A-J. Gemixystus leptos (Houart, 1995). A-B. Coral Sea, 19°40' S, 158°27' E, 245-252 m, holotype MNHN-IM-
2000-970, 4.8 mm; C-D. Protoconch, BATHUS 2, stn DW714, 22°38' S, 167°10' E, 124 m, MNHN-IM-2014-
2453; E-F. KANACONO, stn DW4695, North Iles des Pins, 22°47' S, 167°27' E, 200-290 m, MNHN, 5.1 mm;
G-I. SMIB 8, stns DW182-184, 23°18' - 23°19' S, 168°05' E, 305-367 m, MNHN-IM-2012-32982, 3.7 mm; J.
SMIB 8, stns DW170-172, 23°41° S, 168°00' - 168°01' E, 230-290 m, MNHN, 5.1 mm.
K-T. Gemixystus stimuleus (Hedley, 1908). K-L. New South Wales, Sydney, 22 miles east of Narraben, 146 m,
holotype AMS C.25787, 3.0 mm (photo Alison Miller, AMS); M. Australia, QLD, NE of Cape Moreton, 26°54'-
26°57' S, 153°32' - 153°35' E, 115-124 m, RH, 3.4 mm; N-P, S-T. SMIB 8, stns 146-147, 22°55' S, 168°22' E,
508-532 m, MNHN-IM-2012-33087, 3.5 mm; S-T. Protoconch; Q-R. KANADEEP, Banc Argo, 23°02' S,
159°28' E, 315-1260 m, MNHN, 3.4 mm.
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The genus Gemixystus in New Caledonia
10
Remarks
Gemixystus leptos differs from G. stimuleus in having
a smaller, sharper, acute, shouldered, or more or less
keeled protoconch (Figs 5C-D; 5S-T); the spire is
higher with comparatively narrower spire whorls. G.
leptos also has a broader subsutural ramp, narrower
spines and more widely spaced P1-P2, the shell is
more strongly angulate and the outer apertural lip is
more strongly denticulate within with P1, P2, P3, P4
of which some are split as opposed to P1, P2, P3 in G.
stimuleus.
Only empty shells were recorded from South
Queensland and in shallower depths than the New
Caledonian shells (Houart, 2004). However no
significant differences were detected between the two
populations. The maximum length of 4.9 mm
observed in 2004 is now increased to 5.3 mm in a
specimen collected in New Caledonia.
Gemixystus stimuleus (Hedley, 1907)
Figs 3F; 5K-T
Trophon stimuleus Hedley, 1907: 293, pl. 55, fig. 19.
Type locality. New South Wales, Sydney, 22 miles
east of Narrabeen, 146 m.
Type material. Holotype AMS C.25787.
Other material examined. Australia, Queensland,
off Cape Moreton, 128-183 m, 5 dd (AMS
C.150076), NE of Cape Moreton, 26°54' - 26°57'S,
153°32' - 153°35'E, 115-124 m, 16 dd (AMS
C.321981), 1 dd (RH) (in Houart, 2004).
South of New Caledonia, Norfolk Ridge, SMIB 8,
stns DW146-147, 24°55'S, 168°22'E, 508-532 m,
MNHN-IM-2012-33087, 6 lv, 11 dd.
BATHUS 3, stn DW818, 23°44'S, 168°16'E, 394-401
m, MNHN-IM-2012-32987, 2 lv, 1 dd.
NORFOLK 1, stn DW1692, Banc Eponge, 24°55'S,
168°20'E, 507-967 m, MNHN-IM-2012-33082, 1 lv, 1
dd.
Coral Sea, Lord Howe Rise, KANADEEP, stn
DW4951, 24°12'S, 159°41'E, 270-385 m, 1 dd; stn
DW4962, Banc Argo, 23°02'S, 159°28'E, 315-1260 m,
4 dd.
Distribution. Australia: South Queensland and
Sydney, New South Wales, 115-183 m (dd); New
Caledonia (new distribution record): Coral Sea and
Norfolk Ridge, collected alive in 401-508 m.
Description (from Houart, 2004). Shell up to 3.5 mm
in length at maturity, biconical. Spire high with 1.5
protoconch whorls, and up to 4 broad, weakly
shouldered teleoconch whorls. Suture impressed,
partially obscured by small axial lamellae of following
whorl. Protoconch large, broadly elongate. Whorls
rounded, smooth; terminal varix unknown (eroded in
examined specimens).
Axial sculpture of teleoconch whorls consisting of
high, strong, webbed lamellae: 9 on first whorl, 12 on
second, 15 on third, 11 or 12 on last whorl. Spiral
sculpture of rounded cords: visible spiral sculpture of
first, second and third whorls of P1-P2; last whorl
with P1-P3, decreasing in strength abapically.
Aperture large, broad, rounded. Columellar lip broad,
flaring, smooth, lip partially erect, adherent at adapical
extremity. Anal notch obsolete. Outer lip broad, with
2 weak, broad, low denticles within. Siphonal canal
short, 18-20% of total shell length, narrow, smooth.
Creamy white.
Figure 6. Scale bar 250 µm.
A-B. Gemixystus fimbriatus Houart, 2004. Tasmania, E of D'Entrecasteaux Channel, 44°2.2'S, 146°50.5'E, 176
m, holotype AMS C.322414, 4.1 mm (photo Alison Miller, AMS).
C-F. Gemixystus laminatus (Petterd, 1884). C-D. Tamar Heads, Tasmania, holotype TM E824/8165, 4.9 mm
(photo Simon Grove, TAM); E-F. Australia, Victoria, 30 km SW of Cape Everard, 38°4'S, 149°9'E, 119 m, RH,
4.6 mm; F. Protoconch.
G-H. Gemixystus polyphyllius (Tenison-Woods, 1879). G. Victoria, Muddy Creek, near Hamilton, 37°44'S,
141°56'E, Miocene, holotype AMS C.170873, 5.1 mm; H. Australia, Victoria, Gabo Is. 37°34'S, 149°55'E, 21 m,
AMS C322366, 5.4 mm (photo Alison Miller, AMS).
I-J. Gemixystus recurvatus (Verco, 1909). I. South Australia, 200 fathoms of Beachport, holotype SAMA
D13484, 6.7 mm (photo Shirley Sorokin, SAMA); J. New South Wales, off Sydney, 384 m, AMS C150080, 7
mm (photo Alison Miller, AMS).
K-L. Gemixustus rhodanos Houart, 2004. Australia, NSW, 2.3 km E of Malabar, Sydney. 33°59.45'S,
151°16.8'E, 66 m, holotype AMS C.322835, 5.9 mm (photo Alison Miller, AMS).
M. Gemixystus rippingalei (Houart, 1998). Australia, Queensland, E. of Lady Musgrave Is, 23°62.5' - 23°51.9'S,
152°42.7' - 152°41.7'E, 296 m, holotype AMS C313232, 4 mm (photo Alison Miller, AMS).
N-P. Gemixystus transkeiensis (Houart, 1987). N. South Africa, N Transkei, off Nthlonyane R., 32°17.5'S,
29°03.9' E, 130 m, coarse brown sand, old calcareous fragments, holotype NM C5902, 5.1 mm (photo NM); O-
P. South Africa, Transkei, off Mtamvuna River, 31°10'S, 30°15'E, 120-140 m, paratype RH, 4.5 mm.
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The genus Gemixystus in New Caledonia
12
Remarks. Gemixystus stimuleus is now also recorded
from New Caledonia, in greater depths than in
Australia, but except for a slightly lower spire and
occasionally more numerous axial varices, no other
significant differences were identified.
The New Caledonian form also resembles G.
rippingalei (Houart, 1998) (Fig. 3E; 6M), but G.
rippingalei has a more evenly biconical shell with
obvious, narrower P1-P4 spiral cords on the last
teleoconch whorl and ADP, MP on the siphonal canal.
P1-P4 ending as narrow, open spinelets on the axial
varices, more obvious on the apertural varix with a
longer, narrow P1 spine and shorter P2-P4 spines of
same length. The aperture is also different, being more
ovate in G. rippingalei with 4 narrow D1-D4 denticles
within the outer lip, as opposed to a rounded aperture
with lower denticles in G. stimuleus.
Gemixystus stimuleus from New Caledonia has the
typical sculpture of the species, with relatively broad,
more spaced P1-P2 cords and a narrow and shallow
P3 cord, ending as broad, short open spinelets on the
varices, shorter or obsolete on the apertural varix. The
siphonal canal is smooth.
A
CKNOWLEDGEMENTS
The material newly recorded in the present paper was
sampled during several cruises in the Tropical Deep-
Sea Benthos programme, in particular KANADEEP
(PI: Sarah Samadi), KANACONO (PI: Nicolas
Puillandre) and EBISCO (PI: Philippe Bouchet). For
lists of stations and further information on cruises, see
https://expeditions.mnhn.fr/
For images of the holotypes stored in their institution
we are grateful to Simon Groves (Tasmanian
Museum), Mandy Reid and Alison Miller (Australian
Museum) and Shirley Sorokin (South Australian
Museum). Manuel Caballer (MNHN) provided the
images of the holotypes of Gemixystus calcareus and
G. leptos, E-Recolnat Project: ANR-11-INBS-0004.
The holotype of Gemixystus transkeiensis was
photographed by Igor Muratov (KwaZulu-Natal
Museum, Pietermaritzburg, South Africa) and sent to
the senior author by Alwyn Marais (Edenvale, South
Africa). Thanks also to John Wolff, Lancaster,
Pennsylvania, USA, for checking the English text and
other comments.
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