32 THE NAUTILUS. 



Whiteaves, J. F. — List of some Fresh-water Shells from North- 

 western Ontario and Keewatin. (Ottawa Nat. XX, pp. 31-2, 1906.) 



Explanation op Plate I. 



All the figures are x 2, except Fig. 10, which is x 3. 



Fig. 1. P. bicarinatus aroostookensis Fils. Collins' Mill Pond, 

 Me. 



Fig. 2. P. bicarinatus aroostookensis (topotype). Salmon 

 Brook, Me. 



Fig. 3. P. bicarinatus Say (typical). Delaware River, Phil- 

 lipsburg, N. J. 



Figs. 4 and 5. P. bicarinatus angistomus Hald. Independence 

 Lake, Washtenaw Co., Mich. 



Figs. 6-8. P. bicarinatus unicarinatus Hald (type). Schuyl- 

 kill River, Pa. 



Fig. 9. P. bicarinatus portagensis Baker (cotype). Portage 

 Lake, Me. 



Fig. 10. P. bicarinatus corrugatus Currier (type). Perch 

 Lake, Kent Co., Mich. 



Fig. 11. P. bicarinatus royalensis Walker (type). Siskowit 

 Lake, Isle Royale, Mich. 



Fig. 12. P. bicarinatus percarinatus Walker (type). Crystal 

 Lake, Benzie Co., Mich. 



NOTES. 



An internal septum in Holospira bartschi. — In a specimen 

 of this snail cut open there is a vertical septum across the cavity at 

 about the middle of the eighth whorl. It is concave on the lower 

 side, as in many Urocoptidce. To abandon the early whorls is very 

 common in Antillean and the larger Mexican forms but has not be- 

 fore been noticed in Holospira. The internal column in H. bartschi 

 is very nearly one-third the diameter of the shell at the widest part, 

 but it decreases to about one-fourth in the penultimate whorl. — 



H. A. PiLSBRY. 



