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THE AMEBIC AN NATURALIST [Vol. XLYII 



in the number of body vertebrae (8 in the males and 13 in 

 the females), and the males have on the average .62 less 

 than the females ; and there is a similar variation in the 

 belly scales, the males having .38 less than the females. 

 In the females the number of belly scales varies from one 

 less to one more than the body vertebras, the average 

 being .12 less, and in the males the variation is from one 

 less to two more scales than vertebrae, the average being 

 .12 more. The number of caudal vertebrae is variable (11 

 in the males and 10 in the females), and the males have 

 on the average 6.25 more vertebrae than the females ; and 

 there is a similar variation in the number of subcaudal 

 scutes, 1 the males having 5.62 more than the females. In 

 the females the number of subcaudal scales varies from 1 

 to 3 less than the tail vertebrae, averaging about 2 less, 

 and in the males the scutes vary from 1 to 4 less, average 

 2.63 less. 



It is evident from this summary that the average excess 

 of tail vertebrae over subcaudal scutes (2.63 in the males, 

 2 in the females) is only slightly affected (.12 in either 

 direction) by the discrepancy between the belly scutes 

 and body vertebrae when the whole series are considered, 

 so that the normal relation in the entire series in both 

 sexes is about two less scutes than vertebrae. Further- 

 more the total number of vertebrae and scutes in the males 

 is respectively 5.63 and 5.25 greater than the average 

 number possessed by the females, the decrease (.62 and 

 .38) in the body series in the males not being sufficient to 

 lower the total number to the average number in the 

 females. Still further, a pronounced variation in the 

 total number of vertebrae and scutes in each sex is re- 

 vealed. This variation amounts to 15 vertebrae and 12 

 scutes in the males and 9 vertebrae and 9 scutes in the 

 females, and is of course due to the fact that deviation 

 from the mean in one member is not compensated 

 corresponding deviation from the mean in the op 

 direction in the other member. Thus in the 16 speci 

 the variation on the body and tail is in the same directio 



'It should be stated here that the subcaudal scutes ar< 

 references to the number always refer to the pairs. 



