120 
ZOOLOGICAL GEOGRAPHY. 
[part nr. 
the curious glass -snake, belonging to the Zonuridye ; with Phry- 
nosoma (commonly called horned toads), Callisaurus, Uia, 
Euphryne, TJma , and HolbrooJda, genera of Iguanidae. 
Testudinidse, or Tortoises, show a great development of the 
genus Emys; with Aromochelys and Chelyclra 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 Sirenidse ; Menobranehus 
belongs to the Proteidse ; Amphiuma 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 Scaphiopus, belonging to the Alytidse ; Pseudacris to the 
Hylidae ; and Acris to the Polypedatidas. 
Fresh-water Fishes. — The Near c tic 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 ; Percopsidae, founded 
on a species peculiar to Lake Superior ; Heteropygii, containing 
two genera peculiar to the Eastern States ; Hyodontidae and 
Amiidse, each consisting of a single species. The genera are as 
follows : Faraldbrax , 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 Siluridae. Thaleichthys, one of 
the Salmonidse peculiar to the Columbia river. Moxostoma , 
Pimephales, Zlyborhynchus, Bhinichthys, 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 Cyprinidae. Scaphi- 
rhynchus, found only in the Mississippi and its tributaries, 
belongs to the sturgeon family (Accipenseridse). 
Summary of Near die 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 
