6 Trans. Acad. Sci. of St. Louis 



verse direction (Figs. 1 and 3). In B. americanus the 

 well developed postocular ridge ends laterally in a bifur- 

 cation, one branch running forward and downward be- 

 tween the eye and the tympanic membrane, the other, 

 short but distinct, extending back to the parotid body. 

 In B. foivleri the postocular ridge is less pronounced and 

 the posterior prolongation is lacking. 



Parotid bodies. — In B. foivleri the parotid bodies 

 ^fig. 3) are rather narrow elongated ovals adnate in 

 front, at least laterally, to the postocular ridges. In 

 B. americanus (fig. 1) they are short, generally more or 

 less reniform in outline, and free from the postocular 

 ridge proper, being united only to a prolongation from it. 



Warts. — The warts of B. fowleri are relatively small 

 and with only feeble spines or none at all, those of B. 

 americanus are much larger and often tipped with strong 

 spines. When comparing the males which are of about 

 the same size in the two species the difference in the 

 warts is very noticeable, but in the absence of represen- 

 tatives of both species it would often be difficult to iden- 

 tify a specimen on the basis of warts alone. In B. fow- 

 leri the under parts are finely granular, in B. ameri- 

 canus they are coarsely granular or even spiny. 



Other structural characters. — B. foivleri is in gen- 

 eral appearance more frog-like with a closer fitting skin 

 and smaller, more slender feet than B. americanus. It 

 is a ''much more trim, dapper, active little fellow than its 

 relative." (Allard.) 



Color. Most specimens of B. fowleri show a grayish 

 background with some greenish tints ; only rarely is there 

 a reddish brown cast. In B. americanus the background 

 is most often more or less reddish. In B. fowleri the 

 ground color may change from a light greenish gray to 

 almost black in the course of a few hours. The dark 

 dorsal spots are said (Dickerson) to be more constant in 

 B. fowleri than in B. americanus, there usually being six 

 pairs in the former. A mid dorsal longitudinal gray 

 stripe is more distinct and more constant in B. fowleri 



