1886.] 47 J [Co 



An Analytical Table of the Genera of Snakes. By E. D. Cope. 

 (Bead before the American Philosophical Society, May 21, 1SS6.) 



The following key was prepared as preliminary to a discussion of the 

 genera and species of North American Snakes to be published by the 

 Smithsonian Institution. As this work will not be ready for publication 

 for some months, I publish the present extract from it by permission of 

 the Secretary, Prof. S. F. Baird. It is to be hoped that it may be useful 

 in clearing up some of the obscurity which has existed with regard to the 

 definitions of some forms ; and that it may show that in some instances 

 exact definition requires further separation of such groups, while in others 

 combinations are necessary. 



For the definitions of genera which I have not seen, I am especially 

 indebted to my colleagues in this department, Drs. Peters, Gtinther, Jan. 

 Kreflt, and others. 



OPHIDIA. 



The families of snakes are distinguished by the following osteological 

 characters :* 



A. Opisthotic intercalated in the cranial walls (Angiostomata) . 



* No ectopterygoid ; palatines bounding choanal posteriorly ; eth- 

 moturbinal forming part of roof of mouth ; rudiments of pel- 

 vis (Scolecophidia).\ 



I. Maxillary bone fixed to prefrontal and premaxillary ; a pubis 



Catodonta4 



II. Maxillary bone vertical and free from all others ; no pubis 



EPANODONTA.g 



** An ectopterygoid ; palatines not bounding choanae posteriorly. 



III. Maxillary bone free, horizontal Tortricina. 



f A coronoid bone. 



a. Rudimentary posterior extremities Tortricidce Muller. 



aa. No rudiments of posterior extremities Uropellida Midler. 



B. Opisthotic attached scale-like to cranial walls, and produced 



freely. Ectopterygoid present (Eurystomata). 



IV. Maxillary bone horizontal, in contact with the premaxillary, and fur- 



nished with solid teeth. No rudiments of pelvis Asinea. 



a. Rudiments of posterior extremities (Peropoda). 

 /?. Coronoid bone present. 

 Supraorbital and postorbital bones, and premaxillary teeth present 



Pythonidai Cope. 

 No supraorbitals or premaxillary teeth ; postorbitals present .Boidce Cope. 



* This arrangement was first published by the writer in the Proceedings of 

 the Philadelphia Academy for 18-i-J, p. 230. The definitions of the lower primary 

 divisions were derived from J. Muller. 



tfhe characters of this division as I originally gave them (Proceedings 

 Academy Philada., 18tjl, p. 230) were derived from J. Muller, which have been 

 shown to be partially erroneous by Dumeril and Bibron, and Peters. 



J Includes oiiiy the family Stenostomidce. 



gOne family, the Typhlopidce. 



