7^ oC?^ Vol. 56, pp. 109-128 October 19, 1943 PROCEEDINGS BIOLOGICAL SOCIETY OF WASHn^0NvvJ//7>> /^^ THE MEXICAN SNAKES OF THE GEN^^^^^^ja3RA:' AND CHIONACTIS WITH NOTES ON THE STATUS OF OTHER COLUBRID GENERA.i BY WILLIAM H. STICKEL, JJ. S. Fish and Wildlife Service, Patuxent Research Refuge, Bowie, Maryland. The primary purpose of this paper is to present a revision of the michoacanensis group of the genus Sonora and to discuss the generic position of this group. Circumstances have made it advisable to include all projected taxonomic changes in Sonora, and to give ranges, and localities in Mexico, for the forms of Sonora and Chionactis occurring in that country. The concepts of several species and sub-species of Sonora are altered and the monotypic genus Chionactis is recognized for the very distinct species occipi-alis. A new key to all the snakes of these genera is ap-pended. Notes are given on several other colubrid genera which have been associated with Sonora or are believed to be related to this genus. This paper supplements my pre-vious treatments of the S. semiannulata and S. occipitalis groups (1938 and 1941), and like them is intended as a preliminary work. The species michoacanensis was placed in the genus Contia by the original describer, Duges, and by Cope in two publications, but most authors have followed Boulenger (1896) in assigning it to Scolecophis. Dunn (1928) and Taylor (1937) allocated the species to Sonora, and both writers pointed out the possibility that michoacanensis was also congen-eric with Scolecophis atrocinctus. If this arrangement were followed ' Extracted from material prepared in partial fulfillment of the requirements for the doctoral degree at the University of, Michigan. 22— Proc. Biol. Sop. Wash., Vol. 56, 1943. (109)
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