A new species of the shrimp genus Chorocaris Martin & Hessler, 1990 (Crustacea: Decapoda: Bresiliidae) from hydrothermal vent fields along the Mid-Atlantic ridge

—A new species of the caridean genus Chorocaris Martin & Hessler, C. fortunata, is described from the Lucky Strike hydrothermal vent field along the Mid-Atlantic Ridge in the vicinity of the Azores. The new species differs from the two previously known members of the genus in having an acute conical prominence on the lower angle of the orbit (antennal spine); this spine and the rostrum extend further anteriorly than the anteriormost border of the pterygostomial and ventrolateral region of the carapace. Additional differences include a more stout cheliped, narrower scaphognathite, longer chela on the second pereiopod, and a much smaller size at maturity. The caridean shrimp genus Chorocaris was established by Martin & Hessler (1990) to accommodate C. vandoverae, a small shrimp collected at hydrothermal vent sites in the Mariana Back-Arc Basin, western Pacific. In addition to C. vandoverae, Martin & Hessler (1990) also transferred one Atlantic species of vent shrimp, Rimicaris chacei Williams & Rona, 1986, to Chorocaris. Thus, prior to the current paper there were two recognized species in the genus, with a biogeographically interesting distribution, one known from vent sites in the western Pacific, the other from vents along the Mid-Atlantic Ridge. In June 1993, collections were made using the submarine DSRV Alvin at several vent sites along the Mid-Atlantic Ridge near the Azores. Among the species collected on this cruise were several specimens of a small new species of Chorocaris, which we describe herein. Materials and Methods Shrimp were collected during a series of dives on the American Lucky Strike Cruise (DSRV^/v/« and R/Y Atlantis II. Chief Scientist C. Langmuire, May 27-June 4, 1993, Lucky Strike hydrothermal field, 37''17'N, 32''16'W, 1624-1700 m depth). Although additional specimens from other dives exist in the collections of various researchers (e.g. C. L. Van Dover, curtently at the Duke University Marine Laboratory, Beaufort, North Carolina), all specimens used in this report came from DSRV Alvin Dive 2607, 2 Jun 1993, 1624 m. In addition to the new species, Chorocaris chacei was also present at this site. The material, all of which has been deposited in the Natural History Museum of Los Angeles Count (LACM), with the exception of 5 paratypes sent to the Museum national d'Histoire naturelle, Paris, and to the University of Lisbon, Portugal, VOLUME 108, NUMBER 2 221 consisted of 71 individuals ranging in size from 3.8 mm to 9.4 mm in carapace length (CL) and from 12.0 mm to 33.1 mm total