73 



A single species of tortoise {Chclopus marmoratus) exists iu the Pacific 

 region. 



The fresh-water fish-fauna is much like that of the Central district iu 

 being poor iu types. It adds the viviparous Tharyngognathi of the ftim- 

 ily of EmhiotocUlae, which is represented by a number of species. The 

 marine fauna differs from that of the east coast in the great iiuiiiber 

 of species of Sahno and Sehastes and the variety of types of Cottidac. In 

 its northern regions, the genus Chirus and allies have their peculiar hab- 

 itat. The singular genus Blepsias (related to Coitus) exists on the same 

 coast, and several valuable species of cods [Gadua aiiratuSf G. periscopusj. 

 and Bracliygadus minutus), with the peculiar form Bathymaster, belong 

 especially to the northern coasts. 



The Sonoran region is strongly marked among the faunae already de- 

 scribed. It is deficient in the species of ruminating Mammalia found 

 in the Central, and possesses a smaller number of species of mammals 

 than any of the others. Of birds, a few genera and several species are 

 different from those of the Central ; such are Calllpepla (partridge), Cich- 

 lopsis, Mitrephorus {Tyrannidae), Campylorhynchiis, and Geococcyx. Most 

 of these genera occur iu Mexico, and the last-named in California also. 

 It is in Reptiles that the great peculiarity of this region appears. The 

 following genera are not found in any of the other regions described : 



1 



LiZAEDS. 



Helodernia. 

 Sauromalus. 

 Uma. 

 Coleonyx. 



Serpents. 



Gyalopium. 



Chionactis. 



Sonora. 



EhinocJiihis. 



Chilopoma. 



Eight other genera of Reptilia are peculiar to this fauna and that of the 

 Lower Californian region, under which they are enumerated. Heloder- 

 ma, Coleonyx, and allies of Gyalopium of the above list are more largely 

 developed in species and individuals in the Mexican region of the Neo- 

 tropical realm. Every one of the five genera of serpents of the Sonoran 



