120 ZOOLOGICAL GEOGRAPHY. [part hi. 



the curious glass-snake, belonging to the Zonuridse ; with Phry- 

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

 Euphryne, Uma, and Holbrookia, genera of Iguanidss. 



Testudinidse, or Tortoises, show a great development of the 

 genus Emys; with Aromochelys and Chelydra as peculiar genera. 



Amphibia. — In this class the Nearctic 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 ; Menobranchus 

 belongs to the Proteidse ; Amphiuma is the only representative 

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

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

 have Scaphiopus, belonging to the Alytidse ; Pseudacris to the 

 Hylidas ; and Acris to the Polypedatidse. 



Fresh-water Fishes. — The Nearctic 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 ; Hyodontidse and 

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

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

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

 Eastern States — all belonging to the perch family. Hypodelus 

 and Noturus, belonging to the Siluridre. Thaleiehthys, one of 

 the Salmonidae peculiar to the Columbia river. Moxostoma, 

 Pimephales, ITyborhynchus, Rhinichthys, in the Eastern States ; 

 Ericymba, Exoglossum, Zeucosomus, and Carpiodes, more widely 

 distributed ; Cochlognathus, in Texas ; Mylaphorodon and Ortho- 

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

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

 rhynchus, found only in the Mississippi and its tributaries, 

 belongs to the sturgeon family (Accipenseridse). 



Summary of Nearctic Vertebrata. — 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 



