612 Bulletin American Museum of Natural History [Vol. XLVI 



With the exception of the genus Sator, all of the insular forms are 

 more or less directly allied to those of the peninsula or the Mexican 

 mainland. The faunse of the individual islands are considered below. 

 Sator appears to be a relict form, its survival on two islands (Ceralvo 

 and Santa Cruz) being a fairly conclusive proof of its former presence on 

 the peninsula, probably as a distinct form. Its relations are with a 

 generalized Uta and with Sceloporus utiformis of western Mexico. 



Of the amphibians, all the genera and species have a fairly wide 

 range outside and to the north of Lower California, with the exception 

 of the insular Batrachoseps leucopus. Amides is not yet known from the 

 mainland of the peninsula, but may be expected in the northwestern 

 corner as it reaches the Coronados Islands. Plethodon croceater is prob- 

 ably confined to this area also, Cope's statement (1889, p. 151) that he 

 has seen a specimen from Cape San Lucas being unverified and improbable. 

 Rana aurora draytonii, Scaphiopus* hammondii , and Bufo boreas halo- 

 philus belong to this northwestern fauna and do not range far to the 

 south in Lower California. Hyla arenicolor is known in Lower California 

 only from Ensenada. Four species remain which range throughout the 

 peninsula but with very discontinuous distribution, occurring where 

 suitable habitat conditions exist: Batrachoseps attenuatus, Scaphiopus 

 couchii, Bufo punctatus, and Hyla regilla. Batrachoseps and Hyla are 

 members of the Pacific fauna, not present in the Sonoran subregion, 

 and the Scaphiopus and Bufo are Sonoran forms, absent from the Pacific 

 subregion. The origin of this mixture of faunae will be considered below. 



The genera of lizards (exclusive of the insular Sator) found in Lower 

 California are the following. 



Of these, PhyUodactylus, Ctenosaura, and Bipes are of Mexican 

 affinity, each with a distinct species in Lower California absent from 

 northern Lower California, while PhyUodactylus tuberculosus is identical 

 on the peninsula and in west Mexico. Uma enters the peninsula only 

 in the northeastern area, which is continuous with the Colorado Desert. 

 Coleonyx also, although ranging farther south on the Gulf side of the 



