larger than the anterior. Proximal elements of the tarsus not elongated. 

 Vertebrte numerous, at least 14 in front of the sacrum; these either am- 

 phicoelous or opisthocoelous Ribs present, short. Maxilla present in 

 all except JSiechirus and Siren. Teeth present on maxillaries, vomero-pal- 

 atines, and on the'dentaries, except in Siren. No tympanic cavities or 

 eustachian tubes. Cloaca opening externally by a longitudinal slit. 



The Urodela include about 133 species, distributed principally north 

 of the equator. North America furnishes 54 species, 18 of which, at 

 least, are found in Indiana. 



The order as here defined contains 10 families. Of these, two, the 

 Ccecilidte and the Thoriida3, are not natives of Nf)rth America. 



Key to the N. A. Families of Urodela. 



A. Maxillary bone wanting. External gills present at all times of 

 life. 

 a. Body eel-like. No posterior limbs. Sirenidce, p. 8. 



aa. Body lizard-Ike. Two pairs of limbs. Proteida', p. 10. 



AA. Maxillary bone present. No gills in the adult state. All four 

 limbs present. 

 a. Body extremely elongated. Both pairs of limbs very rudi- 

 mentary. Amphimnidie, p. 12.' 

 aa. Body lizard-like. Anterior and posterior limbs well devel- 

 oped, 

 b. A branchial slit on each side of the neck. Vomero-pa- 

 latine teeth close to and parallel with those of the 

 premaxillaries and maxillaries. 



Gryptobrancludcc p. 15. 

 bb. No branchial slits on the side of the neck. Vomero- 

 palatine teeth considerably behind the premaxillary 

 teeth, 

 c. Parasphenoidal teeth present, forming two brush- 

 like bands along the roof of the mouth. 



Plethodontidce, p. 31. 

 cc. No parasphenoidal teeth. 



e. Vomero-palatine teeth in a transverse row be- 

 tween, or just behind, the choauie. 



Ambystomatida', p. 17. 

 ee. Vomero-palatines in two longitudinal rows 

 along roof of the mouth, on two prolonga- 

 tions backward of the vomers. 



Salavmndridte, p. 44. 



