B3() Illinois Slate Lahoratory of Nalural Hislonj. 



black. Well-defined bands are frequently apparent on the legs 

 of the younger examples, but in adults are generally obscured 

 by the ground color. Tubercle at the base of first toe black- 

 tipped. Tips of fingers and toes also sometimes black-tipped. 

 The males are much smaller than the females, adults of the 

 former not being more than one third the weight of a fe- 

 male with ripe ova. Length of head not much more than half 

 the width of the same. Depth of the head, measuring from 

 the under side of the closed mandible to the highest point of 

 the cranial ridges, about one half the width of the head. 

 Length of head contained about four times in the length of 

 the body from tip of snout to tip of urostyle. 



Length of body of an adult female, 3.62; width of abdo- 

 men, 2.75; depth of abdomen, 1.37. Length of body of an adult 

 male, 3; width of abdomen, 1.31; depth of abdomen, 1. 



Variety americanus 



Cranial ridges not much elevated, not specially enlarged on 

 the back of the head, slightly diverging posteriorly, and, at the 

 back of the head, turning at right angles to the original course 

 and reaching tympanum. Body very stout. Limbs short and 

 strong. Skin very coarsely tuberculate above. Color above 

 olive-brown, spotted as described above; below yellowish white, 

 more or less spotted with black. In this variety the ridges on 

 the head are never as prominent as in the adults of the variety 

 lentiqinosHS. Occasional examples approach the other variety 

 in the prominence of the ridges, but the latter are never so 

 much enlarged behind. Generally the channel of the head is 

 open behind, but in a large male before me it is completely 

 closed by a transverse ridge passing from the posterior end of 

 one longitudinal ridge to that of the other. The colors are, as 

 a rule, darker in this variety. All the Illinois examples which 

 have. been studied, excepting very young ones, are spotted on 

 the skin of the ventral side. These spots are most abundant 

 in the region between the fore legs, and are sometimes so 

 aggregated there as to form a large blotch. Some young ex- 

 amples have no other marks on the skin of the ventral side 

 than this blotch. The throat is generally plain whitish, but 



