PROC. BIOL. SOC. WASH. 106(2), 1993, pp. 251-295 A CHECKLIST OF AND ILLUSTRATED KEY TO THE GENERA AND SPECIES OF THE CENTRAL AND NORTH AMERICAN CAMBARINCOLIDAE (CLITELLATA: BRANCHIOBDELLIDA) Perry C. Holt and Brent D. Opell Abstract.— This paper treats the 90 species of Cambarincolidae known from Central and North America. Each species is illustrated and its synonyms, tax-onomic references, type specimen disposition, and distribution are given. Keys are provided to the family's nine genera and to the 48 species of Cambarincola, 2 species of Ceratodrilus, 1 species of Ellisodrilus, 4 species of Oedipodrilus, 8 species of Pterodrilus, and 1 8 species of Sathodrilus, Magmatodrilus, Tetto-drilus, and Triannulata are each represented by a single species. The branchiobdellidans are obligate epi-zoites on freshwater crustaceans throughout the Holarctic region except, apparently, in Central Asia between the Ural Mountains and the Amur drainage (Holt 1968a). The greatest diversity of families and species is found in North America. This may be an artifact of collecting, as we have less infor-mation from other regions except Europe where only a few species are found. In Asia only Yamaguchi has done any significant work on the Japanese and Korean faunas. Despite the greater body of work on the North American branchiobdellidans, it is likely that only a small fraction of this fauna has been accorded taxonomic treatment. Most genera and species of North American branchiobdellidans are assigned to the fam-ily Cambarincolidae (Holt 1986). The phy-logenetic position and classification of the Branchiobdellida is discussed by Gelder & Brinkhurst (1990), Holt (1986, 1989a), and Sawyer (1986). Methods Types or topotypes of all taxa of the cam-barincolids have been studied in Holt's lab-oratory and detailed methods for preserving and studying specimens are found in Holt (1986). Additional methods include Gelder & Hall's (1990) use of a mixture of clove oil and methyl salicylate (oil of winter-green), as branchiobdellidans, particularly gill-inhabiting forms, are often twisted and distorted when methyl salicylate alone is used in the preparation of entire animals. The use of Nomarski differential interfer-ence contrast optics gives a much clearer view of internal structures in whole animals than does bright field illumination. When time and the availability of specimens per-mit, the worms should be relaxed with an appropriate agent, such as chloral hydrate and, after fixation in alcohol-formalin, lightly stained. For field collection, alcohol-formalin (Holt 1 963) still seems the best and easiest preservative to use. All of the branchiobdellidan material, in-cluding types, studied by Holt and their ac-companying field notes have been deposited in the collections of the National Museum of Natural History, Smithsonian Institu-tion, Washington, D.C., U.S.A. These spec-imens are identified by the accession num-bers (USNM) of the National Museum, or by Holt's accession numbers (PCH . . .). A few paratypes are in the collection of the
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