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

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

 phicwlous or opisthoccelous Ribs present, short. Maxilla present in 

 all except j^ccturus 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 

 Coecilidffi and the Thoriidse, are not natives of North 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 lizarddke. Two pairs of limbs. Proteidce, 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. Amphiunmhe, 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 

 pre maxillaries and maxillaries. 



CryptobranchidK , 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 choarij?e. 



Ambystomatid(e, p. 17. 

 ee. Vomero-palatines in two longitudinal rows 

 along roof of the naoutb, on two prolonga- 

 tions backward of the vomers. 



Salamandridce, p. 44. 



