1917.] NATURAL SCIENCES OF PHILADELPHIA. 15 



Key to the genera. 



a. — Permanent larvae, blind Tyyhhmolge 



aa. — Larva not permanent, develop eyed adults. 

 b. — Tongue free. 



c. — Premaxillaries two Geotriton 



d. — Toes 5, webbed Gyrinophilus 



dd. — Toes 5, free. 

 cc. — Premaxillary single. 



e. — Toes 5, free ..Spelerpes 



ee. — Toes 5, webbed. 



/. — Nostrils small QUdipus 



ff. — Nostrils large Thorius 



eee. — Toes 5, fused '. Q^dipina 



eeee. — Toes 4 • Manculus 



hh. — Tongue not free. 



/. — No premaxillary fontanel. 



g. — Vomerine teeth present , StereocMlus 



gg. — No vomerine teeth Leurognathus 



ff. — Premaxillary fontanel present. 

 h. — Toes 5. 



i. — ^No prefrontal Desmognathus 



a. — Prefrontal present. 

 j. — One premaxillary. 



k. — Blind Typhlotriton 



kk. — Eyes functional Autodax 



jj. — Two premaxillaries. 



I. — Toes fused ? Heptoglossa 



II. — Toes free Plethodon 



hh.— Toes 4. 



m. — Prefrontal present Hemidactylium 



vim. — No prefrontal Batrachoseps 



/ 



It seems useful to add a few remarks on the larvae of some members 

 of the present, as well as allied families. Ambystoma larvae have the 

 dorsal fin-fold extending forward to the head. The larvae of the 

 various species of the same genus seem difficult to separate and are 

 rare in collections, as with the exception of the western species they 

 remain larvae only a few months.* The larvae of Diemictylus are, 

 according to Banta and McAtee, "maculate at an early age, have a 

 dark line through the eye, and when of fair size show the red lateral 

 spots. "^ In many cases the larvEe of species of the Plethodontidce 

 are unknown, and larvae have been seen which could not be identified. 

 The species in the northeast present no great difficulties. The 



* B. G. Smith, Bull. Wiscon. N. Hist. Soc, IX, April, 1911, pp. 14-27, 

 6 Proc. U. S. Nat. Mus., XXX, 1906, pp. 67-83. 



