4 Trans. Acad. Sci. of St. Louis 



rather scattered it may be worth while to review some 

 of the outstanding characteristics of the species, con- 

 trasting it with Bufo americanus. It should be borne in 

 mind that both species are quite variable and that almost 

 any morphological characteristic of the one may occa- 

 sionally be met in the other. There seems to be no defi- 

 nite evidence, however, that the two species hybridize or 

 intergrade in the strictest sense. 



Size. Bufo fowleri is of medium size, with very little 

 difference between the sexes. A typical mated pair, from 

 Forest Park, St. Louis, which produced a large number 

 of fertile eggs when placed in an aquarium were meas- 

 ured from the tip of the snout to the tip of the urostyle. 

 The length of the male was found to be 65 mm., that of 

 the female 68 mm. Bufo americanus on the other hand 

 is larger and shows a very marked difference in the size 

 of the two sexes. A male selected as typical of a con- 

 siderable collection of specimens from Norway, Maine 

 (which appears to be beyond the northern limit of Bufo 

 fowleri), had a length of QQ mm., while a female from 

 the same source and selected in the same way measured 

 90 mm. in length. The weight of the female was more 

 than twice that of the male. The contrast in size be- 

 tween the adult females of the two species is indicated 

 in the accompany sketches which are drawn to scale. 



Surface Anatomy. Shape of the head. — Viewed 

 from above, the head of B. fowleri (fig. 3) appears rather 

 narrow and pointed in front. The eyes generally form 

 part of the outline. In B. americanus (fig 1) the head is 

 very broad and slightly more rounded in front. The eyes, 

 especially in adult females, do not enter into the outline 

 of the head when seen in this position (Dunn). In pro- 

 file (as pointed out by Deckert) the appearance of the 

 two species is very different (figs. 2 and 4). The head of 

 B. fowleri is short and thick with a very blunt snout, that 

 of B. americanus is longer, not so thick, and with a taper- 

 ing snont. This difference is quite as marked in males 

 as in females. 



