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, Plethodon, with the fleshy adherent tongue cf Amby- 
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 
larve lose their branchiw 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 other 
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 obstetricans. The young lose their 
branchiz 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 Hemiductylium, with much the same structure of teeth and 
tongue as the last, has a yvranular, 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. 
Cidipus, 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 Hyle 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 branchie 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 Spelerpes, with much of the general features of the last, has a 
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