PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 1 13(1): 17-23. 2000. Periclimenes murcielagensis, a new species of shrimp (Crustacea: Decapoda: Palaemonidae) living on black coral from the Pacific coast of Costa Rica Rita Vargas Escuela de Biologfa, Universidad de Costa Rica, 2060 San Jose, Costa Rica Abstract. — Periclimenes murcielagensis, new species, a pontoniine shrimp living on black coral colonies, occurs at depths of 25 m at Isla San Pedrito, Archipielago de las Islas Murcielago, Guanacaste, Costa Rica. This new species is most similar to P. veleronis, Holthuis, and P. americanus Kingsley, and is distinguished from these by characters from the rostrum, basal antennular seg-ment, antennular flagellum, and incisor process of the mandible. Shrimps of the genus Periclimenes Cos-ta, 1844, belong to the subfamily Pontoni-ine, and are distributed widely in subtropi-cal and tropical marine waters worldwide. Some species live freely but the majority are associated with other marine inverte-brates. Of the species of this genus known from the eastern Pacific, only P. infraspinis (Rathbun 1902), P. lucasi Chace, 1937, and P. veleronis Holthuis, 1951, have not been reported in association with other inverte-brates (Holthuis 1951). Known associates of these shrimps in the western Atlantic are sponges, gorgonians, actinians, corallimor-pharians, rhizostome scyphozoans, hy-droids, antipatharians, bivalves, ophiuroids and crinoids (Heard & Spotte 1991, Spotte et al. 1994). While conducting ecological studies of soft corals, specimens of an undescribed species of Periclimenes were found living on colonies of black coral (Antipathes pan-amensis Verrill, 1869) at Isla San Pedrito, Archipielago de las Islas Murcielago, Guanacaste, Costa Rica. This new species is described herein. Specimens were collected during SCU-BA dives at 25 m. Plastic bags were placed over black coral colonies and closed with a rubber band. The shrimps and Antipathes panamensis colonies were fixed in a mix-ture of 10% formalin and seawater, the col-onies washed in the laboratory with fresh water, and all the liquid passed through a 0.5 mm mesh. The shrimps were preserved in 70% ethanol. The material is deposited in the National Museum of Natural History, Smithsonian Institution, Washington, D.C. (USNM), and Museo de Zoologia, Universidad de Costa Rica (UCRMZ). Carapace length (CL) was measured from the tip of the rostrum to the posterodorsal margin of the carapace. Periclimenes murcielagensis, new species Figs. 1-5 Material. — Holotype: ovigerous female (CL 7.75 mm), USNM 260931, Isla San Pedrito, Archipielago de las Islas Murcie-lago, Guanacaste, Costa Rica, 25 m, coll. Odalisca Breedy, 24 May 1996. — Para-types: 4 females (CL 7.5-7.9 mm), 2 males (CL 5.256.5), USNM 260932; 9 females (CL 6.25-8.4 mm), 2 males (CL 5.6-6.25 mm), UCRMZ 2247-01, same collection data as holotype. Diagnosis. — Carapace armed with both hepatic and antennal spine; rostrum well developed, reaching end of antennular pe-duncle, usually armed with 8-10 teeth dor-sally and 2-4 teeth on distal half of ventral margin. Antennular peduncle having basal
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