158 



THE CHICAGO ACADEMY OF SCIENCES. 



Penis- 



Locality. 

 Sault St. Marie. 



Siskowit Lake. 



It will be noted that there is a marked difference in the compara- 

 tive lengths of the vas deferens and the prostate duct between the 

 Sault St. Marie and the Siskowit Lake specimens. This may be ac- 

 counted for by the size, the latter individuals being a third larger than 

 the former. 



Distribution of 



SANCT^EMARLE 

 COLUMELLA ~\ 



FIG. 12. 



RANGE: (Figure 12) Northern Michigan and Lake Superior. It 

 has not been found outside of the area of Lake Superior and the 

 northern part of Lake Michigan. It is probably peculiar to the great 

 lakes and hence an inhabitant of the Canadian region and life zone. 



