THE NAUTILUS. 63 



A FEW ADDITIONAL NOTES ON CREPIDTJLA. 



BY REV. HENRY W. WINKLEY', SACO, ME. 



In the August Nautilus Mr. Witmer Stoue makes the statement 

 concerning C. fornicata and C. plana that " the tendency towards 

 convex and concave shells has now become a fixed specific char- 

 acter" and the general description of C. p^a» a grants to that spe- 

 cies an existence on the interiors of other shells and a consequent 

 concave form. 



There is a colony of warm water shells in the Avaters of North- 

 umberland Strait, between Prince Edward's Island and the province 

 of New Brunswick, and this colony is of interest not only for the 

 species which are so cut off from their fellows in the south, but also 

 for a series of interesting Crepidulas. The writer has gathered 

 many specimens of both C. plana and C. fornicata, but in no case 

 was C. plana on the interior, and I recall no concave specimen of 

 either. The specimens of C. plana were in some cases far more 

 convex than the average C. fornicata. To one who has examined 

 this colony the distinction between these species can have no help 

 from convex or concave characters, yet both species are distinct, and 

 while I have no doubt that they are from a common ancestor, it is 

 impossible to count the dwelling place as responsible for the differ- 

 ence. May I also add that there is in my collection from the 

 region named a specimen of C. fornicata which is white, yet bears 

 undoubted characteristics of C. fornicata. 



THE SHELL BEARING MOLLUSCA OF MICHIGAN. 



BY BRY'ANT W^ALKER, DETROIT, MICH. 



Margaritana complanata Bar. Quite abundant and of large size 

 in the Rouge river. Cited also by Currier and De Camp and no 

 doubt occurs generally over the southern part of the State. 



M. delfoiclea Lea. Common all over the State. The small size, 

 peculiar as usual to Detroit river specimens, is also characteristic of 

 specimens from Put-in-Bay, Lake Erie. 



M. Hildrethlana Lea. River Rouge, Wayne county. Cited also 

 by De Camp from Monroe county, and without locality by Sager 

 and Miles. 



