A Note on the Origin of Solenoglyph Snakes

THE PRIMITIVE and isolated position of the genus Causus in the family Viperidae is well known. It is shown by the primitive arrangement of the head shields and the incomplete development of the movable jaw-apparatus, with the skull not shortened to the degree of the normal viperid type. The first investigators of the anatomy of these snakes were interested primarily in the extraordinarily elongate poison glands. Phisalix seems to have been the first to extend the investigation to the characteristic muscle apparatus in the region of the poison gland. I recently criticized Phisalix' attempt to associate the proteroglyph with the solenoglyph groups (Haas, 1931 b). Thanks to the friendly interest of Professor Franz Werner, of Vienna, I have been able to examine a specimen of Causus resimus and compare its cephalic anatomy with that of Causus rhombeatus. It is to be desired that the remaining two species C. defilippi and C. lichtensteini be examined also, but these have not been available.