34 



PROCEEDINGS OF THE ACADEMY OF 



[1883. 



features of the Neotropical realm, and if it lacks some of those 

 of the Nearctic also, its types are mostly representative of the 

 latter rather of the former. I content myself here with confirming 

 this general principle by reference to the principal families and 

 genera of cold-blooded vertebrata. 



R. Nearctica. 



Salmonidae. 

 Cyprinidjfi. 

 Oatostomidse. 



Eanidae. 

 Scaphiopidje. 



Amblystomidte. 



Sceloporus. 

 Eumeces. 



Bascanium. 



Tropidonotus. 



Eutsenia. 



Pityophis. 



Diadophis. 



Ophibolus. 



R. Sonoriana. 



Pisces. 

 Salmonidee. 

 Cyprinidae. 

 Catostomidffi. 



Batrachia. 

 Ranidse. 

 Scaphiopidae. 



Amblystomidfle. 



Reptilia. 



Lacertilia. 

 Sceloporus. 

 Eumeces. 



Ophidia. 



Bascanium. 



Tropidonotus. 



Eutaenia. 



Pityophis. 



Diadophis. 



Ophibolus. 



R. Neotropicalia. 



Characinidge. 



Stenostoma. 



Cvstignathidffi. 



Liocephalus. 

 Mabuia. 



Bothrops. 



Drymobius. 



Helicops. 



Rhadin«a. 



Coniophanes. 



E ry throlamprus. 



Pliocercus. 



Oxyrrhopus. 



Sibon. 



Leptognathus. 



Boa. 



Xiphosoma. 



Stenostoma. 



There are a good many genera which are found in the Sonoran 

 district, which do not occur in other parts of the Nearctic realm. 

 These genera are frequently confined to it, but when they are not, 



