New Squat Lobsters (Galatheidae) from the Pacific 

 Ocean: Mariana Back Arc Basin, East Pacific Rise, and 



Cascadia Basin 



Austin B. Williams and Keiji Baba 



ABSTRACT: Three species of squat lobsters new 

 to science are described and illustrated. Munidopsis 

 marianica, collected with the aid of DSRV Alvin 

 from a hydrothermal vent area in the Mariana Back 

 Arc Basin in the western Pacific, is distinguished 

 from a northeastern Pacific species, M. tuftsi 

 Ambler, by the erectness of its eye spines and orna- 

 mentation of the body, form of telson plates, and 

 spination of dactyls on walking legs. Munidopsis 

 lignaria. collected in association with submerged 

 wood with the aid of RV' Yaquina in trawl samples 

 from the eastern Pacific Cascadia Basin off Oregon 

 and DSRV Alvin from the East Pacific Rise off 

 south central Mexico, is distinguished from its 

 nearest congener, M. ciiiata Wood-Mason, by 

 blunter ornamentation and smaller body size. 

 Munidopsis granosicorium from Cascadia Basin 

 is represented by a unique specimen, the carapace 

 of which has a distinctive unspined ornamentation 

 but a much more broadly triangular rostrum and 

 more pronounced anterior elevation than that of its 

 apparent closest relative, M. follirostris Khodkina. 



On a recent Alvinl Atlantis II expedition to 

 the Mariana Back Arc Basin in the western Pa- 

 cific, 28 dives were made, 6 of them entirely 

 devoted to biology. Those dives focused on 3 

 active low temperature (10°-25°C) vent sites at 

 which anemones, mollusks, shrimps, squat lob- 

 sters, crabs, and other invertebrates were ob- 

 served or collected (R. Hessler'; Hessler et al. 

 1988). We here describe a new species of Muni- 

 dopsis collected during 3 of the dives. 



A subsequent Alvinl Atlantis II e.xpedition 

 (Cruise 118, Leg 32) focused on geological ex- 

 ploration of the East Pacific Rise between lat. 

 10°55'N and irSS'N. Small fields of past and 



present hydrothermal activity were found along 

 the axis of this region, and among samples of 

 biological specimens collected from both vent 

 and nonvent environments was a piece of wood 

 colonized by a variety of invertebrates, including 

 a species oi Munidopsis (see Van Dover 1988). 

 These specimens are identical to specimens 

 taken during extensive collections of benthic 

 megafauna made at stations of the RV Yaquina 

 on the Oregon continental margin and nearby 

 abyssal plains fi-om 1962 to 1983 (Ambler 1980; 

 Carney and Carey 1982; Carey^). A pattern of 

 stations was sampled to determine the distribu- 

 tion and abundance of mega-epifauna and to 

 study the ecological influence at sea of radio- 

 nuclides originating from the Hanford (WA) 

 Nuclear Reservation. Collections at these and 

 other study areas in the region were made with a 

 7. 1 m semiballoon otter trawl (1.3 cm mesh) and 

 with a 3 m beam trawl (1.3 cm mesh) equipped 

 with paired odometer wheels (Carey and 

 Heyamoto 1972). We reviewed all of this mate- 

 rial and here describe the species as new. 

 Finally, a unique but fragmentary specimen of 

 Munidopsis from Professor Carey's sampling 

 progi'am is described. 



Specimens studied, except where otherwise 

 indicated, were from the Oregon State Univer- 

 sity Benthic Invertebrate Museum (OSUBI), 

 CorvaUis, OR; the Museum of Comparative Zool- 

 ogy, Harvard University (MCZ), Cambridge, 

 MA; and the Division of Crustacea of the United 

 States National Museum of Natural History, 

 Smithsonian Institution (USNM), Washington, 

 DC. Types of new species are deposited in crus- 

 tacean collections of the USNM and OSUBI. 



'Robert Hessler. Scripps Institution of Oceanography, La 

 Jolla. CA 92093, pers. commun. September 1987. 



Austin B. Williams, Systematics Laboratory, National 

 Marine Fisheries Service, National Museum of Natural 

 Histon,', Smithsonian Institution, Washington, D. C. 20560. 

 Keiji Baba, Kumamoto University, Faculty of Education, 

 Kurokami 2-chome, Kumamoto, 860 Japan. 



Manuscript Accepted May 1989. 

 Fishery Bulletin, U.S. 87; 899-910. 



Munidopsis marianica New Species 

 Figures 1, 2a, Sa, b 



Material studied. — Western Pacific Ocean, 



^A. G. Carey, Jr., College of Oceanography, Oregon State 

 University, Corvallis, OR 97331, pers. commun. Septem- 

 ber 1988. 



899 



