PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES Vol. 50, No. 7, pp. 185-215, 14 figs., 1 pi., 4 tables. April 27, 1998 A REVISION OF THE SNAKE-EEL GENUS CALLECHELYS (ANGUILLIFORMES: OPHICHTHIDAE) WITH THE DESCRIPTION OF TWO NEW INDO-PACIFIC SPECIES AND A NEW CALLECHELYIN GENUS By John E. McCosker Department of Aquatic Biolog\\ California Academy of Sciences Golden Gate Park, San Francisco, California 941 18 Species of the tropical snake-eel genus Callechelys, family Ophichthidae, subfamily Ophichthinae, are reviewed. An identification key for the species of the tribe Callechelyini and synonymies, illustrations, and diagnoses are provided for each of the valid species of Callechelys: C. bilinearis, C. bitaenlata, C. colostoma, C. cliffi, C. eristigma, C. galapagensis, C. guineensis, C. leucoptera, C. lutea, C. marmorata, C. muraena, and C. springeri. Callechelys papulosa n. sp. is described from Papua, New Guinea, and differs in its morphometry, coloration, and vertebral number. Callechelys randalli n. sp. is described from Fatu Hiva, Marquesas, and differs from the closely-related C. catostoma in its body elongation and higher vertebral numbers. A neotype for C catostoma is designated. Callechelys striatus Smith is synonymized with C. catostoma. Callechelys sibogae Weber is referred to Bascanichthys and C. maculata Chu, Wu and Jin is provisionally referred to Yirrkala. The status of all nominal species of Callechelys is confirmed. Xestochilus gen. nov. is erected for Callechelys nebulosus Smith; it differs from other callechelyins in the unique condition of its snout, lips, dentition, and branchiostegal rays. Its range is extended to include Polynesia, Micronesia, Indonesia and the Red Sea. The distribution of C. catostoma is extended to Hawaii, the western Indian Ocean, and the Red Sea. Received November 19, 1997. Accepted December 19, 1997. Although the snake-eels and worm-eels of the family Ophichthidae are known to have achieved perhaps the greatest diversity of body form and adaptive radiation within the anguilliform fishes, few can be accused of being beautiful. The spe-cies of the genus Callechelys are exceptional, however, in their possession of an elongate mane and generally colorful livery, such that Kaup (1856a, b) was correct in creating the generic name to include the Greek KaXXoc,, meaning beautiful. Since Storey's (1939) review, the spe-cies of Callechelys have only received regional treatments: the western Atlantic (McCosker et al. 1989); the eastern Atlantic (Blache and Cadenat 1971); the eastern Pacific (McCosker and Rosen-blatt 1972. 1995); the western Indian Ocean (Smith 1 962); South Africa (McCosker and Cas-tle 1986); and Australia (McCosker in prep.). The osteology and intrafamilial relationships of several species were described by McCosker (1977) and the leptocephali of the western Atlan-tic species by Leiby (1989). A considerable number of specimens of Callechelys have accu-mulated in recent years, allowing for the first time a revision of the genus. In doing so, I dis-covered that C nebulosus, described by Smith (1958) from the western Indian Ocean, is wide-spread in the lndo-Pacific and has affinities else-where within the tribe Callechelyini.