56 U. S. NATIONAL MUSEUM BULLETIN 206 



In five venulosa from Venezuela the head length averages 28.7 per- 

 cent of the total length, in five mesophaea from Santa Catarina the 

 head length averages 30.5 percent, while in three imitatrix at hand the 

 average is 29.4 percent. With such a slight difference in averages, 

 it is not possible to separate venulosa from the other two species on 

 the length of its head. The head width is a little greater than head 

 length in both venulosa and mesophaea, but nearly equal in imitatrix; 

 hence, this seems to be a valid character for the separation of imitatrix. 



Both of Boulenger's characters for separating venulosa and meso- 

 phaea — heel not reaching beyond eye and tarsal fold being absent in 

 venulosa, the reverse in mesophaea — disappear in a comparison of 

 even a rather small series of the two. The heel may reach to the 

 posterior border of the eye or to the tip of the snout or to any point 

 between in venulosa; in a series of five mesophaea it reaches from the 

 center of the eye to the tip of the snout. The supposed distinction 

 between them as to the development of a tarsal fold also breaks 

 down entirely upon the examination of a few well-preserved examples 

 of either species. In both forms, the tarsal fold may be absent, 

 weak, moderate, or prominent. 



Mirando-Ribeiro (1926, p. 68) states in his key that the toes of 

 mesophaea are webbed up to the disks, while in the other two species the 

 webs extend only to the penultimate phalanx. The toes of all the 

 examples of mesophaea, venulosa and imitatrix at hand are about three- 

 quarters webbed, with the usual slight variation in both directions; 

 hence, this character also is not to be relied on. Even the texture of 

 the skin is not infallible, as it may be either smooth or granular in 

 imitatrix and venulosa but usually thick in either case. The five meso- 

 phaea at hand have a uniformly smooth and relatively thin sldn, which 

 does not seem to possess the heavy glandules found in most specimens 

 of venulosa. 



Besides the texture of the skin, the color pattern seems to differenti- 

 ate mesophaea and venulosa. In mesophaea, the outer corners of the 

 light triangle on the snout continue as definite straight, dark-edged, 

 light dorsolateral stripes, with a fairly uniform dark rectangular area 

 covering the whole of the back, while the arms and legs do not have any 

 distinct pattern of spots or blotches, but remain a uniform brown in 

 alcohol. In venulosa, on the other hand, while the light triangular 

 area on the snout is often quite definite, the dorsolateral light stripes 

 when present are usually very irregular in outline, often running in 

 diagonal branches onto the side, or ending at midbody, giving place to 

 large irregular dark and light blotches which cover the posterior part 

 of the body, and make heavy crossbands on the arms and legs. 



