REPTILIA. 255 



subsequently loses the crest and cartilaginous excrescences of the feet. 

 While it is probable that similar habits are possessed by the second species 

 mentioned, the fact has not yet been observed, and the species only seen 

 in rather dry situations and occasionally exposed to the air during damp 

 weather. This is very rarely the case in other species, which are gene- 

 rally seen only in turning up some log or stone. 



The next genus, Pletkodon, with the fleshy adherent tongue of Amhy- 

 stoma, has two dense patches of card-like teeth on the sphenoid bone. The 

 body is long, slender, and cylindrical, the toes of considerable size. The 

 skin exudes a highly glutinous secretion, and the animal is eminently 

 terrestrial. The eggs are deposited in packages, or aggregations, in moist 

 situations, under stones and logs, not, however, in the water ; and the 

 larvae lose their branchiae at a very early age. The type of the genus is 

 P. glutinosus, and species are found all across the North American 

 continent. 



The genus Desmognathus is highly conspicuous in the possession of 

 strong ligaments, passing from each end of the transverse crest of the first 

 cervical vertebra and inserted into the lower jaw, preventing any othei 

 than a slight opening of the mouth. The occipital condyles, instead of 

 being inclined at an angle with each other and presenting an elongated 

 concavity, are here short cylinders, whose axes are parallel to each other 

 and to that of the body, with the articulating face nearly spherically 

 convex. The species are pretty generally distributed, and inhabit the 

 edges of streams or the waters of marshes, under stones and logs, 

 exhibiting great activity of movement when observed. The eggs are 

 wrapped about the body of the parent, who remains in a cavity of some 

 moist situation until they are hatched, just before which they are probably 

 taken to the water, as in Alytes ohstetricans. The young lose their 

 branchia? at a very early age. It may be mentioned of this genus, in 

 conclusion, that the tongue is attached anteriorly, and free posteriorly, and 

 that there are two narrow plates of weak teeth on the sphenoid bone. 



The genus HeinidactyUum, with much the same structure of teeth and 

 tongue as the last, has a granular, rather dry skin, and but four toes to the 

 hind feet. The tail also presents a curious feature, in being thicker in the 

 middle than at either the base or the end. 



CEdipus, represented by but a single species from Mexico, has the 

 tongue circular, capable of protrusion from the mouth, two contiguous 

 dense patches of card teeth on the sphenoid, and the extremities of the toes 

 dilated into small disks, as in the HylcB or tree frogs. 



Pseudotriton has a structure of tongue and sphenoidal teeth much as in 

 the last, with a thick body, short tail, and simple toes. The species are 

 found in wet situations, under logs or stones resting in the water, or among 

 the loose stones and earth, along the edges, or at the heads of springs. 

 The young retain the branchise for a long time, and pass a year at least in 

 the larval state. The principal species are P. rubrum, P. salmoneum, and 

 P. montanum. 



The genus SpeUrpes, with much of the general features of the last, has a 



459 



