30 THE NAUTILUS. 



by Dr. R. J. Kirkland, after whom the species is named. The 

 Arkansas specimens collected by Ferriss are nearly as large. Toward 

 the east the species seems to diminish rapidly and uniformly in size 

 to an extent which would almost justify their recognition as a vari- 

 etal race. Ohio specimens (fig. 4), collected in considerable numbers 

 by Dr. V. Sterki, are uniformly smaller than the type, while those 

 from Roaches Run, opposite Washington, D. C., and the Potomac 

 River at Alexandria. Va. (figs. 710), are still smaller than those 

 from Ohio. A single example in the collection of the Phil. Academy 

 from Trenton, N. J., is similar to these, but slightly larger. Were 

 it not for the intermediate character of the Ohio shells, these speci- 

 mens would probably be considered a distinct species, characterized 

 by their small size, proportionately higher and narrower shell and 

 more convex anterior slope. But as shown by the figures, the larger 

 and wider Virginian shells grade indistinguishably into the Ohio 

 form, as that does into the immature specimens of the still larger 

 typical form. That this difference in size is a local peculiarity is 

 shown by the fact that in the considerable amount of material col- 

 lected by Dr. Sterki, both in Ohio (several localities) and in the 

 Potomac and its tributary, Roaches Run, near Washington, not a 

 single specimen was obtained which by its greater size would seem 

 to indicate that the balance of the specimens obtained were immature 

 shells. There are also several trays in the Academy's collection 

 from "Washington " similar to those collected by Dr. Sterki. From 

 Michigan and several other western localities, occasional small and 

 medium sized, high, narrow specimens have been noticed which, 

 though larger, seem indistinguishable from the corresponding eastern 

 form (fig. 10). But these do not seem to be persistent varieties in 

 any one locality, being usually associated with the usual form of 

 kirklandi; but rather sporadic individuals which for some reason 

 have failed to develop normally. It is the occurrence of such speci- 

 mens, together with the inability to find any marked specific charac- 

 ter in the eastern forms, except the difference in size, that has caused 

 me to refrain from giving them varietal rank until additional ma- 

 terial shall give a better opportunity to pass _ipon the exact relations 

 to these various forms. 



PLATE II. 



Figs. 1-3. A. Mrkhmdi Walker (type), Grand River, Kent Co., 

 l^fch. 



