AMPHIBIANS 139 



like the] adult and without a keeled tail. The first stage lasts 3 or 4 

 months; the second lasts 2 or 3 years, and at the end of it the animal 

 again becomes aquatic. 



Subspecies of T. viridescens 



T. V. viridescens Raf, Eastern States and Canada. 



T. V. symmetricus (Harlan). Similar to T. viridescens, but with the 

 red spots forming a continuous or a broken line: coastal plain. North 

 Carolina to Florida. 



T. louisianensis (Wolterstorff ) . Similar to T. viridescens, except 

 that the red spots are inconspicuous or absent, and are not ringed with 

 black: Gulf Coast to Tennessee and Kansas. 



T, torosus (Eschscholtz). Body rather stout; tail long, with a 

 wide keel above and below; color brown above and yellow beneath; 

 length 170 mm.; tail 92 mm.: Pacific slope, from Alaska to Lower 

 California, in ponds and streams; no terrestrial form present. 



Family 3. Ambystomidae. — Body of medium size; digits 4-5; a 

 transverse series of teeth, more or less interrupted, on the hinder margin 

 of the vomers; tongue thick, free in front; vertebras amphicoelous; 

 carpus and tarsus ossified; eyelids present; lungs and ypsiloid cartilage 

 present; costal grooves prominent: 3 genera in the United States; 

 habitat usually terrestrial. 



Key to the United States Genera of Ambystomidae 



ai Lungs rudimentary; ypsiloid cartilage aborted; on Pacific slope, i. Rhyacotriton. 

 ao Lungs and ypsiloid cartilage (Fig. 65) well developed. 



bi Tail dorsally thin and flattened 2. Dicamptodon. 



b2 Tail dorsally thick and glandular 3. Ambystoma. 



1. Rhyacotriton Dunn. Lungs very small; ypsiloid cartilage 

 aborted; nasal bones absent: i species. 



R. olympicus (Gaige). Color black above; length 1 25 mm. : Olympic 

 Mountains, Washington, in mountain streams. 



2. Dicamptodon Strauch. Lungs and ypsiloid cartilage normal: 

 nasal bones present: i species. 



D. ensatus (Eschscholtz) {Chondrotus tenehrosus Baird & Girard). 

 Body very large and massive; legs stout; color reddish brown, mottled 

 above; length 250 mm.; tail 100 mm.; costal grooves 12, obscure; 

 parasphenoid narrow: coastal region of Pacific slope, from southern 

 California to British Columbia. 



3. Ambystoma Tschudi. Lungs and ypsiloid cartilage well 

 developed; premaxillary fontanelle small or wanting; nasals present; 



