138 REPTILES AND BATRACHIANS. 



Scaphiopus couchii Baird, 1854. 



Monclova, Savineto, San Luis Potosi, and nine leagues 

 south of San Luis Potosi. 



Amblystoma mexicanum Shaw ; Cope. 



The colors vary from very light with brown spots to 

 dark brown. This species may be distinguished from A. 

 mavorlium, in the same stages, by the slenderness of the 

 band of palatine teeth. Most often, in specimens half 

 grown or more, these teeth form a single series, rarely 

 more, a condition only reached by mavortium on losing 

 the gills. The multitude of small black spots also aids in 

 characterizing A. mexicanum; the other is more likely to 

 be nearly or entirely without spots on the belly. The pal- 

 atine teeth of the larval A. tigrinum are like those of A. 

 mavortium, but the latter appears to remain longer or be- 

 come larger in the larval stages, often becoming sexually 

 mature without transforming. 



