PROC. BIOL. SOC. WASH. 101(3), 1988, pp. 682-692 NOTES ON SOME RHYSSOPLAX FROM THE PACIFIC OCEAN (MOLLUSCA: POLYPLACOPHORA: CHITONIDAE)

Robert C. Bullock

Abstract. — Taxonomic comments are presented for the following Rhyssoplax from the Pacific Islands: R. discolor (Souverbie, 1866), R. ectypa (Rochebrune, 1884), and R. rhynchota (Rochebrune, 1884) from New Caledonia; R. spino- setata (Bergenhayn, 1930), from the Fiji Islands; R. whitleyi Iredale & Hull, 1932, from the Cook Islands; R. perviridis (Carpenter, 1865) from the Society Islands; Rhyssoplax sp. from the New Hebrides east to the Samoan Islands;

and the widespread R. pulcherrima (Sowerby, 1 842), which ranges from South- east Asia to New Caledonia. The latter species is conspecific with R. excellens Iredale & Hull, 1926, C. excellens capricornensis Ashby, 1928, and R. nier- strasziana Kaas, 1957. Rhyssoplax ectypa, which has been considered a junior synonym ofR. discolor for nearly a century, is recognized as a separate species. Chiton (Clathropleura) pacificus Thiele, 1910, is a junior synonym of R. per- viridis. Thiele's (1910) published description and figure of the type specimen of R. rhynchota were erroneously based on R. crawfordi (Sykes) from South Africa.

Species of the polyplacophoran genus sary precaution, for his diagnoses ofChitons Rhyssoplax Thiele, 1893, are sporadically generally defy identification of either genus represented among malacological collec- or species." Iredale & Hull (1932:158) com- tions from the islands of the central Pacific mented on the problems associated with type Ocean, and their taxonomy is poorly under- material in the Museum National d'His- stood. The predominant reason for this sit- toire Naturelle in Paris: "Rochebrune ran uation is the inadequate collections avail- riot among these shells in the Paris Mu- able for study. Large, well preserved seum. Using a classification ofhis own which collections from all major island groups will has defied interpretation, he lost, mislaid be required before sound taxonomic con- and transferred labels and specimens, de- clusions can be reached. scribing the types of former workers under Study of many Pacific Rhyssoplax is also different genera and then renaming his own perplexing due to the inadequate published new species until there is no confidence in work of the past. The works of Rochebrune any specimens of this class in that Mu- (1884 and other papers) especially have seum." Bullock (1972) noted that some of proved to be troublesome. Pilsbry (1893: this material is present in the Dautzenberg 151), in a discussion of Rochebrune's use collection at the Institut Royal des Sciences of the controversial name Gymnoplax, cor- Naturelles de Belgique in Brussels. rectly observed the outcome of Roche- The zoogeography and phylogenetic re- brune's efforts: "It should be noted that the lationships of Pacific Island Rhyssoplax will irrepressible Rochebrune still uses Gym- prove to be of great interest. Preliminary noplax in a generic sense, in order presum- examination of the distributional patterns ably, to disguise his species;— an unneces- indicate that a few species, for example R. VOLUME 101, NUMBER 3 683 pulcherrima (Sowerby, 1842), are broadly ZMK, Universitetets Zoologiske Museum, distributed across several island groups, Copenhagen; ZMU, Uppsala Universitets while a larger numer of species appear to be Zoologiska Museum, Uppsala. endemic to a single island group. Examples of the latter group include: R. discolor (Sou- Gtrm^ Rhyssoplax T\i\Q\Q, 1893 verbie, 1866), known only from New Cal- Rhyssoplaxlih\e\Q, 1893:368. Type species, edonia; R. whitleyi Iredale & Hull, 1932, Chiton affinis Issel, 1869, by declaration found only in the Cook Islands; and R. spi- of the ICZN, Opinion 951. nosetata (Bergenhayn, 1930), reported only from the Fiji Islands. Major conclusions, Remarks.— \n general, the name Rhys- however, must be made only after the tax- soplax has been used for small to moderate- onomy of the group is better known. sized, non-New World polyplacophorans that are otherwise similar in shell and girdle Materials and Methods scale morphology to the genus Chiton from the New World. Employment of Rhysso- Specimens were examined from the ma- plax at the generic level is not accepted by jor collections of the U.S. and Europe listed all polyplacophoran workers. Malacologists below. Additional material was received from Australia and New Zealand for the from the Western Australian Museum and most part have championed this use, while the Australian Museum. Girdle scales of se- others, for example Kaas & Van Belle (1981), lected specimens were prepared for scan- have used Rhyssoplax as a subgenus of ning electron microscopy (SEM) following Chiton Linnaeus, 1758. Substantial radular procedures described by Bullock (1985). differences exist between Chiton and Samples were mounted on aluminum stubs Rhyssoplax: in Chiton the distal edge of the using double coated tape, and coated with centro-lateral tooth is perpendicular to the carbon and gold/palladium in a Denton DV- longitudinal axis of the animal, while in all 502 vacuum evaporator. All work was done Rhyssoplax the distal edge is parallel to the using an ISI MSM-3 SEM located in the longitudinal axis. Furthermore, the denticle Department of Zoology at the University of cap of the major lateral tooth of Rhyssoplax Rhode Island. is rather short with a circular black tab dis- The following abbreviations are used: tally on the anterior surface. In Chiton the AMS, Australian Museum, Sydney; ANSP, denticle cap tends to be elongate and the Academy of Natural Sciences of Philadel- black tab is usually elongate. It is advisable phia; BMNH, British Museum (Natural to consider these groups as separate genera History), London; ICZN, International Code within the subfamily Chitoninae. ofZoological Nomenclature; IRSN, Institut Royal des Sciences Naturelles de Belgique, Rhyssoplax discolor (Souverbie, 1866) Brussels; MCZ, Museum of Comparative Fig. 13 Zoology, Harvard University, Cambridge; MHNB, Museum d'Histoire Naturelle de Chiton discolor Souverbie [in Souverbie &

Bordeaux; MNHNP, Museum National Montrouzier], 1866:252, pi. 9, figs. 1, la d'Histoire Naturelle, Paris; NRS, Naturhis- (ins. Art, I'Archipel caledonien; lectotype, toriska Riksmuseet, Stockholm; USNM, selected by Strack [1986], in MHNB). National Museum of Natural History, Chiton tuberculosus Souverbie [in Souver- Washington, D.C.; WAM, Western Austra- bie & Montrouzier], 1866:251, pi. 9, fig. lian Museum, Perth; ZMA, Zoologisch Mu- 3 (ins. Art, I'Archipel caledonien; holo- seum, Amsterdam; ZMHU, Zoologischen type in MHNB). Museum, Humboldt-Universitat, Berlin; Chiton (Rhyssoplax) discolor Souverbie.— 684 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

Figs. 1-9. Shells of Pacific Rhyssoplax: 1, Rhyssoplax perviridis Carpenter, Arue, Society Islands, 11 mm [curled](USNM672794); 2,HolotypeofC/z//o«;7em>/^/sCarpenter, Tahiti, Society Islands, 11mm (MCZ 141 125); 3, Rhyssoplax ectypa (Rochebrune), New Caledonia, 20.5 mm (BMNH); 4, Syntype of Lepidopleurus ecyptus Rochebrune, 20 mm (MNHNP); 5, Chiton rhynchotus 'Rochebrune' Thiele [=R. crawfordi (Sykes)], 9.5 mm VOLUME 101, NUMBER 3 685

Figs. 10-15. Scanning electron micrographs of girdle scales of Pacific Rhyssoplax: 10, Rhyssoplax rhynchota (Rochebrune), W end, Ricaudy Reef, Noumea, New Caledonia, 29 Ix (ANSP 271045); 11, Rhyssoplax pul- cherrima (Sowerby), 3 mi [4.8 km] S ofAirport Beach, Phuket Is., Thailand, 8 1 x (ANSP 286765); 1 2, Rhyssoplax spinosetata (Bergenhayn), Korolevu, Viti Levu, Fiji Islands, 95 x (ANSP 236891); 13, Rhyssoplax discolor (Souverbie), near radio station. Bale Ouemo, Noumea, New Caledonia, 46 x (ANSP 271200); 14, Rhyssoplax ectypa (Rochebrune), 0-4 ft [0-1.2 m], Thio, New Caledonia, 107x (ANSP 238361); 15, Rhyssoplax sp., E side of Vailele Bay, Upolu Is., Western Samoa, 169x (ANSP 198086).

Strack, 1986:195, fig. 4a, b [description; The New Caledonian R. discolor is not types fig'd.]. very similar to R. coryphea (Hedley & Hull, Remarks. —Rhyssoplax discolor is a com- 1912) from Norfolk Island, as Iredale & Hull mon species that varies considerably in col- (1932) suggested. Rhyssoplax coryphea is or. Risbec (1 946), who reported on the anat- more highly elevated, more elongate, and omy of this species, noted that on the rocks has longitudinal ribs which only partly ex- at Noumea R. discolor is second in abun- tend across the valve. The girdle scales of dance only to Acanthopleura gemmata R. discolor (Fig. 13) characteristically ex- (Blainville, 1825). hibit a broad shelf across the apical surface Pilsbry (1894) erroneously believed that and have many apical pustules; in R. co- Lepidopleurus ectypus Rochebrune is con- ryphea this shelf is nearly lacking and the specific with this species, and all subsequent pustules are limited to a narrow region at authors have accepted this conclusion. the apex. However, an examination of syntype ma- Locality records.— Nqw Caledonia: Koe terial of L. ectypus [IRSN and NMHNP] Reef, 2 mi [3.2 km] SSE Touho; Touho Bay; (Fig. 4) revealed that it is distinct and not Koe, near Touho; Thio; Yate (all ANSP); at all closely related to R. discolor (see re- Noumea Harbour (AMS); Port Ngea, Ma- marks under R. ectypa). genta, Noumea (ANSP); Baie des Isoles,

[curled] (MNHNP); 6, Rhyssoplax rhynchotus (Rochebrune), barrier reef, 5 mi [8 km] WSW Gatope Is., Voh, New Caledonia, 9.5 mm (ANSP 269722); 7, Rhyssoplax spinosetata (Bergenhayn), N shore of Port Ellington, NNE Viti Levu, Fiji Islands, 17.5 mm (MCZ 279505); 8, Rhyssoplax whitleyi Iredale & Hull, 0.25 mi [0.4 km] N of Matavera, NE Rarotonga, S Cook Islands, 1 1 mm (MCZ 252808); 9, Rhyssoplax sp., E side of Vailele Bay, Upolu Is., Western Samoa, 7 mm (ANSP 198086). 686 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

Ouemo, Magenta, Noumea (AMS); S side, and continuous over callus as small holes Bale de Citron; Baie de Citron, Noumea, in in posterior depression. Primary slit-ray with

1-6 ft [0.3-1.8 m] (both ANSP); lie Cesar, longitudinally elongate slits on callus, more Anse Vata, Noumea (AMS); mouth of circular, smaller slits in posterior depres- stream entering Anse Vata Bay, Noumea, sion. Secondary slit-ray absent. in 2-6 ft [0.6-1.8 m]; Tonghouen Bay, 45 Girdle scales: Moderate in size, rather km N of Noumea; Plage de Foe, Bourail; S ovate, with reticular sculpture predominate side, Gatope Is., Voh; SW side. Isle Mouac, except near apex where large, fairly close- Poume; 2 mi [3.2 km] N of Poume (all packed nodules are arranged in rows. Apical

ANSP). shelf lacking (Fig. 1 4). Remarks.— Rhyssoplax ectypa is distin- Rhyssoplax ectypa (Rochebrune, 1884) guished from R. discolor by its more sharply

Figs. 3, 4, 14 defined lateral triangle, more abrupt post- mucral slope on the posterior valve, nar- Lepidopleurus ectypus Rochebrune, 1884:37 rower ribs of the central area which are (Nouvelle Caledonie; syntypes in IRSN strongest near the lateral triangle, and by and MNHNP). the fact that as the animal grows, additional Description. —Animal medium in size, up ribs of the lateral triangle and end valves to 38 mm in length, 1 9 mm in width. Valves begin separately between existing ones, not subcarinate, angle about 90°. Anterior valve as bifurcations of previous ribs. The girdle straight to convex; post-mucral slope of scales of the two species greatly differ (Figs. posterior valve abrupt, concave at first, con- 13, 14). In R. ectypa the scales are ovate vex ventrally. Mucro moderately sharp, rather than roundly triangular and the char- often worn, centrally located on posterior acteristic apical shelf of R. discolor is lack- valve. Jugal region smooth. Central areas ing. The apical pustules of R. ectypa are with numerous, fine, slightly irregular, linearly arranged, not random as in R. dis- longitudinal ribs, up to 28 per side; dorsal color. Certain structural aspects, such as the edge somewhat sloping, ventral edge more sharply defined lateral triangle and the man- abrupt; first few dorsal ribs not reaching ner by which new ribs are added, indicate preceding valve. Lateral triangle sharply that R. ectypa is most closely related to the elevated, with 3-6 nodular, radiating ribs; more northern R. komaiana (Is. «fe Iw. Taki, nodes on posterior rib longitudinally elon- 1929), which may be differentiated by its gate. Terminal areas with similar radial more inflated girdle scales and more pro- sculpture, up to 25 on anterior and posterior nounced ribs of the central areas of the in- valves. New radial ribs begin anew between termediate valves. existing ribs. Shell color grayish white with Rhyssoplax ectypa has not been recog- a few darker speckles at jugum or, more nized as a valid taxonomic entity since its commonly, cream orange or reddish brown. original description by Rochebrune (1884). Girdle very light orange or alternately band- At least five species of Rhyssoplax are now ed white and light orange. Interior of valves reported from New Caledonia: Rhyssoplax white to dull greenish white. subassimilis (Souverbie, 1866), known only Insertion plates: Intermediate valves with by the holotype (Strack 1986); the abundant a single slit per side; insertion teeth well R. discolor (Souverbie); and the uncommon grooved, but not deeply pectinate. Anterior R. ectypa, R. rhynchota{Koc\\€bnxnQ, 1884),

valve with 10 teeth; posterior valve with 13 and R. pulcherrima (Sowerby, 1 842). Gym- teeth. noplax ludoviciae Rochebrune, 1884 [syn- Hypostracum: Jugal tract in central type IRSN], stated to be from New Cale- depression with numerous transverse slits donia, is Chiton (Chondroplax) granosus 1

VOLUME 101, NUMBER 3 687

Frembly, 1827, from the Pacific coast of 2, fig. 36; pi. 7, figs. 195-199 (Insel San- South America. Gymnoplax alphonsinae guisiapo, 12 m; Saleyer; syntypes in Rochebrune, 1884 [syntypes IRSN and ZMA). Non Reeve, 1847, nee Dupuis, MNHNP], also stated to be from New Cal- 1918. edonia, is actually Rhyssoplax aerea (Reeve, Rhyssoplax excellens Iredale & Hull, 1926: 1847) from New Zealand. 181, pi. 19, figs. 22, 27, 40 (Damley Is- Distribution. —Rhyssoplax ectypa is land, Torres Strait; type in Macleay Mu- known only from New Caledonia. seum, Sydney) [description].— Iredale & Locality records. —New Caledonia: Hull, 1927:116, pi. 13, figs. 22, 27, 40.- (BMNH, IRSN, MNHNP); 0-4 ft [0-1.2 m], Mackay, 1934:150, pi. 16 Thio, New Caledonia (ANSP). Chiton (Rhyssoplax) excellens capricornen-

sis Ashby, 1928:169, pi. 12, figs. 1, 13 Rhyssoplax sp. (Capricorn Group; location of type un- Figs. 9, 15 known). Rhyssoplax nierstrasziana Kaas, 1957:85 Remarks.— T\iQ collections of the ANSP (new name for C. reticulatus Nierstrasz, and USNM include a few examples of small 1905, non Reeve, 1847). Rhyssoplax that possibly are juveniles of one or more species. The shell sculpture is Remarks. —Rhyssoplax pulcherrima dif- reminiscent of that of R. ectypa from New fers from all other Rhyssoplax, and all other Caledonia. The girdle scales from the dif- Chitoninae, by its cancellate sculpture ofthe ferent localities vary in the size of the apical central areas. This species has been rede- pustules, the linearity of these pustules, the scribed on a number of occasions because existence of small riblets that extend from it seems that authors have been unwilling the pustular region ventrally to the reticular to recognize its broad distribution. Austra- sculpture, and the presence in some cases lian workers in particular have maintained of broader ribs. I figure an example from that their specimens represented a species the Samoan Islands (Fig. 9) and a girdle different from the one in the Philippine Is- scale from it (Fig. 1 5). lands. Locality records.— New Hebrides: rocky Pilsbry (1893) considered this species to reef flat, ESE of Inyeung Is., Aneityum be an Ischnochiton, but an examination of (USNM). — Tonga Islands: Niuafoou Is. the radula, especially the denticle cap of the (USNM).— Hoom Islands: over the outside major lateral tooth, indicates its chitonid fringing reef, NW of Mua, Alofi (USNM).- affinities. A study of the shell morphology Samoan Islands: Asili, Tutuila (USNM); of the Siboga Expedition material revealed Pago Pago, Tutuila (USNM); east side of that Chiton reticulatus Nierstrasz, 1905, is Vailele Bay, Upolu Is. (ANSP). this species, and its renaming by Kaas (1957) was unjustified. Rhyssoplax komaiana (Is. Rhyssoplax pulcherrima (Sowerby, 1842) & Iw. Taki, 1929), which occurs sympatri- Fig. 1 cally with R. pulcherrima in at least Malay- Chiton pulcherrimus Sowerby, 1842:103 sia, the Philippines, and possibly south to (Gindulman, ins. Bohol, Philippinarum; the Admiralty Islands (ANSP 182204), dif-

type in BMNH). -Leloup, 1952:34, pi. 1, fers by its rounded valves and lack of can-

fig. 2; pi. 4, fig. 1 ; text-fig. 1 3 [girdle ele- cellate sculpture. The prominent central ribs ments and esthetes fig'd.]. on the girdle scales of R. pulcherrima (Fig.

Ischnochiton pulcherrimus (Sowerby).— 1 1) easily distinguish this species from other

Pilsbry, 1893:130, pi. 27, fig. 47, 48. carinate Rhyssoplax. Chiton reticulatus Nierstrasz, 1905:81, pi. Distribution. — A. tropical species, Rhys- 688 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON soplax pulcherrima occurs from Thailand to banded with dark brown. Other specimens the Philippine Islands and south to Queens- much lighter, usually yellowish green mac- land, Australia, the New Hebrides, and New ulated with small greenish brown markings, Caledonia. or yellowish white with similar maculations Locality recor^is.— Thailand: Pulau Tan- with lateral areas orange; girdle alternately ga, Butang Group (USNM); coral rubble reef, banded yellowish white and dull green. In- 3 mi [4.8 km] S of Airport Beach, Phuket terior of valves blue or white with bluish

Is., Andaman Sea (ANSP); Koh Chang, Gulf green to dull green streak extending from of Siam (ZMK).— Malaysia: Pulau Siburu, mucro along slope of posterior depression. N of Sipora, SW of Sumatra (USNM); Pi- Insertion plates: Intermediate valves with sang Is. (IRSN); N shore of Toba Is., N end a single slit per side, occasionally doubly of Aru, Molucca Is. [5°21'S, 136°27'E] slit; insertion teeth highly grooved, not (WAM).—Philippine Islands: Gindulman, deeply pectinate. Anterior valve with 9-12

Bohol Is. (BMNH); rock shore at Cabcaben, teeth; posterior valve with 1 1-15 teeth. SE Bataan, Luzon Is. (ANSP).— New Heb- Hypostracum: Much of central depres- rides: Anelgauhat, Aneityum Is., on Turbo sion with irregular thin grooves and slits. marmoratus L. (ANSP).— New Caledonia: Primary slit-ray well developed, with prom-

4-7 ft [1.2-2.1 m], barrier reef, 5 mi [8 km] inent diagonal slits. Secondary slit-ray lack- WSW of Gatope Is., Voh, SW New Cale- ing. donia (ANSP). Girdle scales: Moderately large, rather smooth; fine reticular sculpture ventrally; Rhyssoplax spinosetata central area smooth with obsolete stria- (Bergenhayn, 1930) tions; apical area sharply defined by close-

Figs. 7, 12 packed pustules of moderate size. Remarks. —A comparison of Bergen- Chiton spinosetatus Bergenhayn, 1930:24, hayn's type specimen ofR. spinosetata with pi. 1, figs. 17-28; pi. 2, figs. 29-31 (Viti additional specimens collected from the Fiji Levu, Fiji Islands; type in NRS). Islands has firmly established the identity Description. — AmvcidX medium to small ofR. spinosetata, although slight differences in size, reaching a length of 22 mm, a width exist between populations. Rhyssoplax spi- of 14 mm. Valves fairly carinate, angle about nosetata appears to be related most closely 100°. Anterior valve straight to convex; post- to two New Zealand species, R. stangeri mucral slope of posterior valve straight to (Reeve, 1847) and R. canaliculata (Quoy & slightly concave. Mucro rather blunt, slight- Gaimard, 1835). ly anteriorly acentric on posterior valve. Ju- Distribution. —Rhyssoplax spinosetata is gal region smooth; central area with up to apparently endemic to the Fiji Islands. 20 well formed longitudinal ribs per side, Locality records. —Fiji Islands: Kaba, Viti usually all reaching preceding valve; dorsal Levu (ZMU); N shore of Nananu-i-ra Is., 3 edge of each rib somewhat sloping, lateral mi [4.8 km] N of Port Ellington, NNE Viti edge abrupt. Lateral triangle with 5-8 ra- Levu (ANSP, MCZ); fringe reef, Korolevu, diating, occasionally bifurcating rows of low, Viti Levu (ANSP, MCZ). broad nodules. Terminal areas with similar radial sculpture, up to 41 rows on anterior Rhyssoplax perviridis (Carpenter, 1865) valve, 29 on posterior valve. Shell color Figs. 1, 2 variable. Some specimens dark brown with scattered lighter, maculated areas and dark Chiton (Lophyrus) perviridis Carpenter, girdle of yellowish white scales irregularly 1865:511 (Central Pacific [type locality VOLUME 101, NUMBER 3 689

here restricted to Tahiti, Society Islands]; idis (Fig. 2), formerly in the Pease collection, holotypeMCZ 141125). is in the Museum of Comparative Zoology. Chiton {Clathropleura) pacificus Thiele, Although the label and the original descrip- 1910:93, pi. 10, figs. 1-4 (Huahine and tion state the locality to be "Central Pacif- Anaa [Society Is.]; type in ZMHU). ic," Pease (1872) mentioned that the spec- imen was from Tahiti. The type locality is Description. — Xmrm\ rather small, at- therefore restricted to Tahiti, Society Is- taining a length of 13 mm, a width of 8.5 lands. Thiele (1910), who was no doubt un- mm. Valves subcarinate, angle about 105°. aware of the identity of Carpenter's species, Anterior valve straight; post-mucral slope described Chiton pacificus on the basis of of posterior valve concave. Mucro moder- specimens from Huahine and Anaa, also in ately sharp, anteriorly acentric on posterior the Society Islands; an examination of valve. Jugal region smooth. Central areas Thiele's type indicates it is conspecific with with up to 17 longitudinal ribs, the more R. perviridis. dorsal ones not reaching preceding valve; Rhyssoplax perviridis differs from the dorsal surface of each rib sloping, ventral Rhyssoplax ofneighboring island groups, but edge abrupt. Lateral triangle elevated, with appears to be most closely related to R. lins- 4-6 weak, low-noduled ribs. Terminal areas leyi Burghardt, 1973, from the Hawaiian with similar radial sculpture; ribs obsolete. Islands and i?. w/zzY/^y/Tredale & Hull, 1932, Shell color usually yellowish white; lateral from the Cook Islands. Rhyssoplax linsleyi edge of each longitudinal rib translucent has more even radial sculpture and the lon- brown or dark green. Small, irregular green- gitudinal ribs of the central areas are some- ish brown flecks on lateral triangle; larger what better formed. Rhyssoplax perviridis is splotches along anterior edge of lateral tri- easily differentiated from R. whitleyi by angle and occasionally along posterior edge. lacking the stronger longitudinal ribs of the Some immature specimens smoother, to- central area and the low, but prominent, tally green. Girdle alternately banded light nodules of the lateral triangle. The girdle blue-green and yellowish white. Interior of scales of all three species are quite similar, valves white. except that those ofR. linsleyi have thin ribs Insertion plates: Intermediate valves with in the central area while those of R. pervir-

a single slit per side; insertion teeth highly idis and R. whitleyi have broad ribs. grooved, moderately pectinate. Anterior Distribution. —Rhyssoplax perviridis is valve with 10-11 teeth; posterior valve with known only from the Society and Tubuai 11-12 teeth. Islands. Hypostracum: Jugal tract of central Locality records. —Society Islands: (MCZ, depression with scattered transverse slits; USNM); W of Motu Tapu, Bora Bora Is.; entire central depression nearly transparent. Arue, Tahiti; E side of Taunoa Pass, Tahiti Primary slit-ray with prominent slits on cal- (all USNM); fringe reef, opposite pass, Pu- lus, a row of irregular small holes in pos- neavia, Tahiti (ANSP, MCZ); Huahine; terior depression. Anaa (both ZMHU).— Tubuai Islands: W Girdle scales: Rather large, roundly tri- of wharf, Moerai, Rurutu (USNM). angular, moderately inflated; reticular Rhyssoplax whitleyi Iredale & Hull, 1932 sculpture ventrally; 14-17 broad ribs on Fig. 8 central area, thinning near apex; small num-

ber of close-packed pustules at apex; apical [?] Chiton (Clathropleura) alphonsinae shelf barely evident. 'Rochebrune' Thiele, 1910:93 [in part]. Remarks.— ThQ unique type of i?. pervir- Non Rochebrune, 1884. 690 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

Rhyssoplax whitleyi Iredale & Hull, 1932: as Anthochiton, Tegulaplax Iredale & Hull, 145, pi. 9, figs. 15, 16 (Rarotonga, Cook 1926, Delicatoplax Iredale & Hull, 1926, Islands; type in AMS [not seen]) [descrip- and Mucrosquama Iredale & Hull, 1926, tion]. must await detailed radular and anatomical studies. Remarks. —Rhyssoplax whitleyi is distin- guished fi-om other Rhyssoplax from the Rhyssoplax {Anthochiton) rhynchota central Pacific by its yellowish brown and (Rochebrune, 1884) blue coloration and by the prominent low Figs. 6, 10 nodules on the lateral triangle. Its girdle Gymnoplax rhynchotus Rochebrune, 1884: scales are moderately large, roundly trian- (Nouvelle Caledonie; type not found gular with reticular sculpture evident ven- 39 in the MNHNP).-Pilsbry, 1894:100. trally and at sides; there are 8-10 broad ribs Rhyssoplax rhynchotus (Rochebrune).— on the central area and moderate-sized pus- Risbec, 1946:163, fig. 18 (anatomy, es- tules on a flattened apical area. Rhyssoplax thetes, radula). whitleyi differs from R. perviridis by having Non Chiton (Clathropleura) rhynchotus better formed longitudinal ribs on the cen- 'Rochebrune' Thiele, 1910:92, pi. 9, figs. tral areas. In R. spinosetata from the Fiji 52-55 [=Rhyssoplax crawfordi (Sykes, Islands, the nodules are less pronounced and 1898)]. the scales (Fig. 1 2) very weakly striated, not distinctly striated as in R. whitleyi. Also, the Description. —Animal rather small, apical pustules of the girdle scales ofR. spi- reaching a length of 9.5 mm, a width of 5.5 nosetata are sharply limited to the apex, and mm. Valves subcarinate, angle about 90°. not converging into the central area ribs as Mucro rather blunt, anteriorly acentric on in R. whitleyi and R. perviridis. posterior valve. Jugal region smooth. Cen- Distribution. —Rhyssoplax whitleyi has tral areas with up to 12 well formed longi- only been recorded from the Cook Islands. tudinal ribs per side. Lateral triangle smooth, Locality records.— Cook Islands: Avatiu often somewhat inflated. Terminal areas Harbor to Motu Toa, Rarotonga (USNM); smooth. Shell color tan, yellowish green, or 0.25 mi [0.4 km] N of Matavera, NE Rar- light orange, often with irregular darker otonga (ANSP, MCZ); Koromiri Is., SE markings. Girdle similarly colored. Interior Rarotonga (ANSP); Avaavaroa Passage, S of valves white. Rarotonga (ANSP); fringe reef off" Aroa Insertion plates: Intermediate valves with

Creek, SW Rarotonga (ANSP). a single slit per side; insertion teeth ap- pearing smooth but obsoletely grooved. Subgenus Anthochiton Thiele, 1893 Hypostracum: Jugal tract with numerous, faint transverse grooves. Primary slit-ray Anthochiton Thiele, 1893:377. Type species with many longitudinally elongate slits. by monotypy, Anthochiton tulipa (Quoy Girdle scales: Moderate in size, ovate to (feGaimard, 1835). rectangular; reticular sculpture ventrally,

Remarks.— The name Anthochiton has about 2 1 broad, close-packed ribs on central been used for Rhyssoplax-like species that and apical areas (Fig. 10). have a smooth lateral triangle and end Remarks. —Rhyssoplax rhynchota is valves. It appears useful at this time to use characterized by its small size, strong lon- this name to denote a separate lineage with- gitudinal ribs ofthe central areas, and slight- in the genus Rhyssoplax that is character- ly inflated lateral triangle. The specimen ized by these features. The taxonomic status marked "type" in the MNHNP is not this ofnomina associated with Rhyssoplax, such species. This latter specimen was figured and VOLUME 101, NUMBER 3 691

described by Thiele (1910) as an example the Royal Society of South Australia 52:167- of Rochebrune's species, but an examina- 173, pi. 12 [in part]. Bergenhayn, J. R. M. 1930. Die Loricaten von Prof tion of the valves (Fig. 5), which clearly have Dr. Sixten Bocks Pazifik-Expedition 1917-1918 a concave lateral triangle, and the girdle mit spezieller Beriicksichtigung der Perinotum- scales reveal it to be a young example ofR. bildungen und der Schalenstruktur.— Goteborgs crawfordi (Sykes, 1898) from South Africa. Kungliga Vetenskaps-och Vitterhets-Samhalles The nearly smooth insertion teeth of R. Handlingar, femte Foljden, (B) 1(12), 52 pp., 3 rhynchota are unusual for Chitoninae. A pis. Bullock, R. C. 1972. Notes on the genus Chiton in check of the radular proved it to be typically the western Indian Ocean (Mollusca: Polypla- chitonid. cophora).— Occasional Papers on Mollusks, Distribution. —Rhyssoplax rhynchota oc- Museum of Comparative Zoology, Harvard curs from the Bismarck Archipelago south University 3:237-251, pi. 44.

. 1985. The Stenoplax to New Caledonia. limaciformis (Sowerby, 1832) species complex in the New World (Mol- Locality r^cor^is.— Bismarck Archipela- lusca: Polyplacophora: Ischnochitonidae).— Ve- Ireland Caledo- go: New (BMNH).—New liger 27:291-307, 24 figs. nia: (MNHNP); Oubatche (AMS); N tip of Carpenter, P. P. 1865. Description of two species of Santa Marie (Isle Ngea), Magenta, Noumea; Chitonidae, from the collection of W. Harper Pease, Esq.— Proceedings of the Zoological So- 0-3 ft [0-0.9 m], W end, Ricaudy Reef, ciety of London for 1865:511-512. Noumea; 4-7 ft [1.2-2.1 m], barrier reef, 5 ICZN [International Commission on Zoological No- mi [8 km] WSW Gatope Is., Voh (all ANSP). menclature]. 1971. Opinion 951. Rhyssoplax

Thiele, 1 893 (Amphineura): designation ofa type species under the plenary powers.— Bulletin of Acknowledgments Zoological Nomenclature 28:18-19. Iredale, T., & A. F. B. Hull. 1926. A monograph of For assistance during my visits to their the Australian loricates. VI.— Australian Zool- institutions and for the loan of specimens, ogist 4:164-185, pis. 18-20.

. I gratefully acknowledge: K. Boss and R. , & 1927. A monograph of Australian Turner (MCZ), H. Coomans (ZMA), T. loricates. Sydney, 168 pp., 21 pis.

, & . 1932. The loricates of the Neo- Kariing and C. Holmquist (NRS), R. Kilias zelanic region. —Australian Zoologist 7: 1 1 9-1 64, (ZMHU), J. Knudsen (ZMK), E. Leloup pis. 7-10.

(IRSN), B. Metivier and A.-M. Testud Kaas, P. 1957. Notes on Loricata. 5. On some preoc- (MNHNP), G. Davis and R. Robertson cupied names. — Basteria 21:83-87. Belle. 1981. living (ANSP), J. Rosewater, C. Roper, and H. ,& R. A. Van Catalogue of chitons (Mollusca: Polyplacophora). Rotter- Rehder (USNM), J. Taylor, K. Way, and J. dam, W. Backhuys, 144 pp. Peake (BMNH), W. Ponder (AMS), B. Wil- Leloup, E. 1952. Polyplacophores de I'Ocean Indien son and L. Joll (WAM). Although in general et des cotes de ITndochine fran9aise. — Me- collections of Pacific island Rhyssoplax are moires de ITnstitut Royal des Sciences Natu- meagre, I especially wish to acknowledge relles de Belgique, Deuxieme Serie, Fasc. 47, 69 6 pis. the collections that were made possible by pp., Mackay, J. 1 934. Notes on a rare loricate, Rhyssoplax the efforts of G. and M. Cline, V. Orr Maes, excellens Iredale and Hull. — Memoires of the and R. Ostheimer (ANSP) and H. Rehder National Museum, Victoria 8:150-153, pi. 16. (USNM); without this material the present Nierstrasz, H. 1905. Die Chitonen der Siboga-Ex- study would have been impossible. pedition.— Siboga-Expeditie Monographie 48: 1- 114, 8 pis. Pease, W. H. 1872. Polynesian Chitonidae. — Amer- Literature Cited ican Journal of Conchology 7:194-195. Pilsbry,H.A. 1892-1894. Polyplacophora. -Manual Ashby, E. 1928. Notes on a collection of chitons ofConchology 14:1-128 [1892], 129-350 [1893]; (Polyplacophora) from the Capricorn Group, 15:1-133 [1894].

Queensland.— Transactions and Proceedings of Risbec, J. 1946. Etudes anatomiques sur les amphi- 692 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

neures de la Nouvelle-Caledonie.— Journal de Strack, H. L. 1986. Notes on New Caledonian chi-

la Societe des Oceanistes 2:129-190, pi. 2. tons. I. The species described by St.-M. Sou-

Rochebrune, A. T. de. 1884. Diagnoses d'especes verbie. - Basteria 50:193-198, 5 figs.

nouvelles de la famille des Chitonidae (Deux- Thiele, J. 1893. Polyplacophoren. Pp. 353-401 and ieme supplement). — Bulletin de Societe Philo- pis. 30-32 in F. H. Troschel, Das Gebiss der matique de Paris (7) 8:32-39. Schnecken, volume 2. Berlin, Nicolaische Ver- Souverbie, M., & R. P. Montrouzier. 1866. Descrip- lagsbuchhandlung.

tions d'especes nouvelles de I'Archipel caledo- . 1910. Revision des Systems der Chitonen, nien.— Journal de Conchyliologie 14:248-261, Il.-Zoologica 22:71-132, pis. 7-10.

pi. 9. Sowerby, G. B. 1842. Descriptions of four species of Department of Zoology, University of the genus Chiton, brought by H. Cuming, Esq. from the Phihppine Islands.— Proceedings of the Rhode Island, Kingston, Rhode Island Zoological Society of London for 1841:103-104. 02881.