544 URODELA [CH. 



so-called amphicoelous vertebrae, i.e. vertebrae in which the inter- 

 vertebral discs remain cartilaginous, not true amphicoelous vertebrae 

 as in fish. Molge (Diemyctilus) mridescens is the common Water- 

 newt of Lower Canada. It is a member of the same genus as the 

 English Newt which has been selected for detailed description, but 

 unlike its English congener the American species does not develop 

 a crest in the breeding season. These Newts are representatives of 

 the SALAMANDRINAE distinguished by having the vomeropalatine 

 teeth in a longitudinal row and by possessing opisthocoelous vertebrae. 

 The family DESMOGNATHINAE are closely allied to the Amblystoma- 

 tinae, but differ from the latter in possessing a cluster of teeth on 

 the parasphenoid in addition to the transverse row of vomero- 

 palatine teeth and in having opisthocoelous vertebrae. The 

 species of this family are common Water-newts in the Eastern 

 United States. Desmognathus nigra, the Black Salamander, occurs 

 near Montreal. The PLETHODONTINAE includes the American Cave- 

 and Land-newts which rarely enter water but wriggle about actively 

 on land. These Newts resemble the Desmognathinae in their teeth, 

 but differ in possessing amphicoelous vertebrae. Although the 

 most terrestrial in their habits of the New World Urodela, these 

 animals and some of the Desmognathinae have undergone an extra- 

 ordinary modification in their respiratory system. The lungs have 

 disappeared and the septum between the auricles has become ab- 

 sorbed : so that the animals depend for their oxygen entirely on their 

 skin and the lining of the pharynx, the walls of which still execute 

 active respiratory movements. This curious association of terrestrial 

 habits with the absence of lungs suggests the idea that the lung in 

 such Urodela as retain it may be chiefly used as a hydrostatic 

 organ like the air-bladder of fish, for were it of prime importance as 

 a respiratory organ it would be difficult to explain its disappearance 

 in terrestrial forms. Spelerpes includes the Cave-newts, of which 

 there are twenty species in America and one isolated species in 1 

 Italy. In these animals the tongue is long and not adherent to the 

 floor of the mouth. It can be suddenly protruded and is used to 

 catch insects in the same way as the tongue of the Anura. This is 

 an exceptional action amongst Urodela, most of which seize their 

 prey with the jaws. Plethodon erythronotus has the typical Urodele 

 tongue. This is the common Land-newt in the neighbourhood of 

 Montreal, being found under old logs and in other damp situations. 



