122 THE NAUTILUS. 



by Baker,' in his recent work on the " Mollusca of the Chicago Area." 

 Lea's figure, 2 which is copied by Try on, is either very poor or else 

 represents an abnormal specimen. Binney's figure, which is stated 

 to be from one of the types, is more accurate and represents the spe- 

 cies as usually found at the present time. 



Campeloma milesii has not as yet been recorded from outside the 

 state of Michigan. In that State it has a well-defined and somewhat 

 peculiar distribution and, wherever found, seems to preserve its essen- 

 tial characteristics as fully as any of the other recognized species of 

 the genus (figs. 1, 2, 3, 4, 7, 8 and 9). It is an interesting coinci- 

 dence, if nothing more, that its range is substantially the same as that 

 of Limnsea catascopium and Physa ancillaria magnalacustris, which 

 are the characteristic univalves of the shores of the Great Lakes and 

 of the rivers and lakes in close proximity to them. The localities 

 thus far recorded for milesii are the Detroit River, Saginaw Bay, 

 Carp Lake and Crooked Lake Emmet county, Branch Lake Antrim 

 county, North Lake on Beaver Island in Lake Michigan and the 

 Pine River Marquette county. In most of these localities it is asso- 

 ciated with O. decisa and in some with C. rufa. On the other hand, 

 the range of O. subsolida in Michigan is quite different. This species 

 on the eastern side of the State has not been found north of the Clin- 

 ton River. On the western side it is abundant in the St. Joseph and 

 Grand Rivers and apparently ranges as far north as Charlevoix, 

 which is the only place where it has been found associated with 

 milesii. Neither form has been reported from the interior of the 

 State, and subsolida does not $eem to be found in waters of any of 

 the Great Lakes. From this, it is evident that the ranges of the two 

 forms are quite different and only impinge in the extreme northwest- 

 ern part of the lower peninsula. 



Compared with C. subsolida, as found in the southern part of the 

 State (fig. 11), and which is quite typical, it differs both in form and 

 texture. Subsolida is a large,, thick, heavy shell, with a blunt apex, 

 sinuous lip and with a heavy white deposit on the parietal wall. It 

 is practically free from erosion. On the other hand, milesii has a 

 thin shell, a regularly-tapering, acute spire, a thin, transparent pari- 

 etal callus, a much less sinuous lip, and is usually only about half the 



'Moll, of Chi. Area, p. 361 (1902). 

 "Observations, XI, pi. 24, fig. 114. 



