31 



burrowiug iu the ground. He says it has been known to burrow in soft 

 ground to the depth of three feet. 



Family V. PLETHODONTID^. 



(Includes Prof . Cope' s families Plethodontid(je, Desmognafhidce, and Thoriidce,^' 



r>l, 33). 



Body salamandrine in form. No persistent gills or gill-slits. Verte- 

 brae amphiccBlous or opisthocoelous. Teeth on posterior edge of vomers. 

 Parasphenoidal teeth present. Tongue extensively free on sides or all 

 round. Carpus and tarsus cartilaginous. 



Key to the Subfamilies of Plethodontidce.^ 



A. Vertebrje amphicoelous. Plethodontinee, p. 31. 



AA. Vertebrre opisthocoelous. 



a. Carpus and tarsus cartilaginous. Desmognathince, p. 42. 



aa. Carpus and tarsus osseous. Extralimital. Thoriince. 



Subfamily PLETHODONTIN^. 

 Vertebrae amphicoelian. Carpus and tarsus cartilaginous. 



Key to the N. A. Genera of Plethodonthue. 



A. Tongue free along the sides, but not in front, 

 a. Posterior digits 4. 



b. Costal grooves 18-31 ; Pacific States. Batraehoseps. 



bb. Costal grooves 13. Seynidactylium, p. 32. 



aa. Posterior digits 5. 



b. Mandibular teeth small, numerous, terete. 



c. Premaxillaries not ankylosed ; costal grooves 10 to 19. 



Plethodon, p. 33. 



cc. Premaxillaries ankylosed ; costal grooves 17 ; color, pale 



yellow. Georgia. Stereochilus. 



bb. Mandibular teeth, few, small, knife-shaped. Pacific States. 



Autodax 



"The three subfamilies of Plethodontidaj are founded on internal characters, and re- 

 <iuire some dissections. These, however, are not difficult to make. By makintr a short in- 

 cision along the back of the specimen in liand, dressing away the muscular tissue down to 

 the vertebral column, and then sharply bending the back so that two of the vertebra sepa- 

 rate, it may be seen whether the anterior rounded head of the vertebrae is made of cartilsge 

 or bone. If it is ol cartilage, the vertebne are amiihiccelous; if of bone, opi.«thoe(olous. In 

 either case, the posterior end of the vertebral centrum is concave. In like manner, the 

 wrist and ankle may be dissected and the determination made whether the nodules found in 

 them are composed wholly of cartilage or are bony. Since, however, we have no species of 

 Thoriinir, this examination is not necessary. It may facilitate the determinttion to recollect 

 that the species of Denmognithps resemble in easily observed characters the species of 

 Plethodon on]y, and the descriptions of these should be carefully scanned. 



