1918.] 



NATURAL SCIENCES OF PHILADELPHIA. 



317 



The head and back are blackish brown, fading downward and back- 

 ward to dark grayish brown, the tail paler. The sole has lateral 

 bands somewhat darker than the central field (No. 119,048). 



Genitalia (fig. 11) generally similar to S. hachitana. The penis 

 is very slender, its retractor muscle longer; penis-papilla slender, 

 smooth, with tapering end. A short flagellum is present. The 

 epiphallus is nearly as long as the penis. The vagina is generally 

 longer than the penis. 



In one specimen dissected, Station 20 (fig. 12a), the penis is about 

 a third longer, its papilla very long, three times the usual length or 

 more. The flagellum also is much longer. Such differences would 

 usually be thought specific, yet I have not found any differences in 

 the shells from this localitv. 



Fig. 12. a, Genitalia of S. cosrulifluminis ra>\, 119,047, from Station 20, 

 Blue River, h, S. hinncyi franciscana No. 119,044. 



Measurements of genitaUa of aS. cceruliflmninis. 



Collecting Station 18 19 16 20 



Penis 8.5 7.5 7 12 



Penis-papilla 3 3.5 4 11 



Epiphallus 8 6 7 8.7 



Flagellum 0.6 0.7 0.5 2 



Retractor , . . . 10 13 



Vagina 15 14 8 9.5 



Museum No 119,048 119,042 119,046 119,047 



