16 BULLETIN 160, UNITED STATES NATIONAL MUSEUM 



Class AMPHIBIA Linnaeus 



1758. Amphibia Linnaeus, Systema naturae, ed. 10, vol. 1, p. 194. 



The amphibians have a skull that is characterized by several 

 morphological features. The chrondrocranium is platybasic; the 

 quadrate is immovably united with the cranium by an otic process, 

 which joins the otic capsule, and by an ascending process, which 

 reaches to the pterygoid; the stapes occupies the fenestra vestibuli 

 of the otic capsule; and there are two occipital condyles. 



Of the three recent orders included in this class, the Salientia 

 (frogs and toads) are far more numerous as regards genera and species 

 than either the Caudata (salamanders) or the Apoda (caecilians). 

 The Salientia alone are treated in this report. 



Order SALIENTIA Laurenti 



1768. Salientia Laurenti, Synopsin reptilium, p. 24. 



The members of this order have the hind limbs developed for 

 leaping, and they are much longer and stronger then the forelegs. 

 The most striking skeletal feature found in the Salientia is the fusion 

 of the caudal vertebrae into a single rod, the coccyx or urostyle. The 

 skull is characterized in part by the absence of basioccipital, supra- 

 occipital, and supratemporal bones, by the ankylosis of the frontal 

 and parietal bones, and by the lack of any connection between the 

 stapes and the quadrate. Vomerine and palatine bones are present 

 but are not united with each other, and the latter bounds the choana 

 posteriorly and joins the pterygoid externally. The astragalus and 

 calcaneum are elongated and form a distinct section of the hind limb, 

 the tarsus. 



The classification of the Salientia adopted is based on slight modi- 

 fications of internal structure, and some of the forms can only be 

 distinguished from closely related species by close scrutiny. The 

 minute details of internal structure, such as the relations of the 

 several elements that compose the ventral portion of the shoulder 

 girdle, the shape of the sacral diapophyses, the articular relations 

 between the sacral vertebra and coccyx, the number of presacral 

 vertebrae, the shape of the terminal phalanges, and the presence or 

 absence of intercalary disks, can only be determined by dissection. 

 Other characters employed are the presence or absence of maxillary, 

 vomerine, and parasphenoid teeth, the attachment of the tongue, the 

 presence or absence of parotoid glands, the presence or absence of 

 lumbar glands, the shape of the pupil of the eye, the extent of the 

 web between the digits of the fore and hind feet, the characters fur- 

 nished by the texture of the skin, and the color patterns. 



The present report is based on the critical study of nearly 2,200 

 specimens from the mainland of Mexico. Seven families of Salientia 

 are represented in Mexico by a total of 19 genera and 65 species. 



