NATURAL SCIENCES OP PHILADELPHIA. 313 



There were four species of Batrachia of the following range : 



Peculiar to the Peninsula, Hyla curta Cope, s. n. 

 Extending to Pacific district, " regilla B., G. 



Extending to South Central, Scaphiopus couchii, (var. varius C ) 



" " " Bufo punctatus B., G. 



The relations of the Sonoran district fauna, then, to that of Cape St. Lucas, 

 are as follows : 



Total number Sonoran 68 



Confined to it 45 



Total number Cape St. Lucas 34 



Confined to it 19 



Common to the two 10 



Cape St. Lucas sp. in South Central district 4 



" " Pacific district 3 



The only genus occurring at Cape St. Lucas which does not exist elsewhere 

 in the Regio Nearctica, is Ctenosaura, which is Mexican. 



Prof. Baird has regarded (Proc. Acad. 1859, 300) the Sonoran and Lower 

 Californian provinces as identical, and has pointed out the slight affinity of 

 the latter to the Pacific district. It appears from the preceding that, in re- 

 spect to the reptiles, they constitute provinces nearly as distinct from each 

 other as the Sonoran is from the Central, a conclusion agreeing with that 

 attained by Dr. John L. LeConte from a study of the Coleoptera, (vid. Proc. 

 Acad. 1861, 335). That these, and the Pacific province, are more nearly re- 

 lated to each other than to the Eastern province, is sufficiently apparent on 

 general Herpetological and other grounds, as set forth in Prof. Baird's masterly 

 review of the distribution of North American Birds, Sillinian's Journ. Sci. 

 and Arts, 1866. 



Dr. Giintber has indicated the Tropic of Cancer as the approximate division 

 line between the Nearctic and Neotropical Regions ; the writer (1. c. 1861, 

 306) has regarded tbis as the parallel of its eastern extremity, and placed the 

 western several degrees further north. More recently Prof. Baird (1. c.) has 

 indicated a less oblique division, raising the eastern extremity to the mouth 

 of the Rio Grande, and terminating it on the west at Guaymas. While he 

 characterizes the line as "arbitrary" for the birds, it is much less so for 

 terrestrial vertebrates ; in these the transition of faunse is striking and quite 

 abrupt. 



Description o/Hyla curta Cope, supra. 



Form stout, size small, breadth of jaws entering total length two and two- 

 third times. Males without gular vocal vesicle. Tongue nearly one-t'iird 

 free. Femur posteriorly unicolor ; basal fold weak. A dark labial border 

 and band from nostril to axilla, above ashy brown, with a dark interocjlar 

 triangle and a broad dorso-lateral band on each side, "often broken into 

 elongate spots. Limbs punctulate and cross-barred. 



Muzzle projecting beyond nares not very prominent ; cantbus rostralis well 

 defined, straight, loreal region not concave. Eyes little prominent, diameter 

 less than distance between origins of canthus rostralis, three times that of 

 tympanum. Vomerine fascicles entirely between nares, choanre small. Skin 

 smooth to sparsely and finely tuberculate above. Digits sto.ut, dilat-ations 

 well defined except on the inner anterior; all the latter free, the posterior 

 not elongate, webbed to base of second phalanx. Hind foot measures one 

 and two-thirds width of head ; the heel extended reaches anterior margin of 

 orbit. The sacral diapophyses are slender, like those of H. pickeringii. 

 Tarsal fold distinct, cuneiform process small ; heel extended reaches anterior 

 orbit. 



The groin is sometimes mottled with black, and the sides often with brown, 



1866.] 



