120 ZOOLOGICAL GEOGRAPHY. [part hi. 



the curious glass-snake, belonging to tlie Zonuridte ; with Phry- 

 nosoma (commonly called horned toads), Callisaurus, Uta, 

 Mtphryne, Uma, and Holhroohia, genera of Igiianidse. 



Testudinidee, or Tortoises, show a great development of the 

 genus Emys ; with Arornochdys and Chelydra as peculiar genera. 



AmjJhibia. — In this class the JSTearctic region is very rich, 

 possessing representatives of nine of the families, of which two 

 are peculiar to the region, and there are no less than fifteen 

 peculiar genera. Siren forms the family Sirenidee ; Menolrancluis 

 belongs to the Proteidte ; AmpJiiuma is the only representative 

 of the Amphiumidae; there are nine peculiar genera of Sala- 

 mandridse. Among the tail-less batrachians (frogs and toads) we 

 have ScapMojnis, belonging to the Alytidte ; Pseudacris to the 

 Hylidffi ; and Acris to the Polypedatidce. 



Fresh-ivater Fishes. — The ISTearctic region possesses no less than 

 five peculiar family types, and twenty-four peculiar genera of 

 this class. The families are Aphredoderidse, consisting of a 

 single species found in the Eastern States ; Percopsidse, founded 

 on a species peculiar to Lake Superior ; Heteropygii, containing 

 two genera peculiar to the Eastern States ; Hyodontidee and 

 Amiidse, each consisting of a single species. The genera are as 

 follows: Paralahrax, found in California; Huro, peculiar to 

 Lake Huron ; Pileoma, Bolcosoma, Bryttus and Pomotis in the 

 Eastern States — all belonging to the perch family. Hyjmdelus 

 and Noiurvs, belonging to the Siluridie. Thaleichtliys, one of 

 the Salmonidaj peculiar to the Columbia river. Moxostoma, 

 Pimephales, Hyhorhynchus, RliinicMhys, in the Eastern States; 

 Ericyiiiba, Exoglossum, Leucosoiiuts, and Carpiodes, more widely 

 distributed ; Coclilognathus, in Texas ; Mylaphorodon and Ortho- 

 don, in California ; Meda, in the river Gila ; and Acrochilus, in 

 the Columbia river — all belonging to the Cyprinidae. Scaphi- 

 rhynchus, found only in the Mississippi and its tributaries, 

 belongs to the sturgeon family (Accipenseridse). 



Summary of Kearetic Vertehrata. — The Nearctic region 

 possesses 24 peculiar genera of mammalia, 49 of birds, 21 of 

 reptiles, and 29 of fresh-water fishes, making 123 in all. Of 

 these 70 are mammals and land-birds, out of a total of 242 



