No. 433.] SNAKES OF SOUTHERN MICHIGAN. 9 



in number of scale rows is not correlated with size, for although 

 the nine aberrant females average larger than most female 

 sipedons, three of them average only 650 mm. and the seven 

 aberrant males average 17 mm. less than the average male 

 sipedon. From these figures it can be easily shown that about 

 68 males in 100 will have the normal number of scale rows and 

 labials, but of 100 females only 36 can be expected to be nor- 

 mal in both respects. On looking over my list of 52 males 



and 38 females, I find that this is about the proportion which 

 prevails ; there is, however, one less normal male and two 

 more normal females than would be expected. 



6. Greater Variability of Lower Jazv. — In comparing the 

 variability of the sexes, the interesting fact was brought to 

 light that the number of labials in the lower jaw is much more 

 variable than the number in the upper jaw ; that is to say, it is 

 much more common to find 8—8 upper labials than 10—10 

 lower. Thus, of the 52 males, 50, or 96 per cent, have the 



