OF CONCIIOLOGY. 



81 



ON THE SHELLS OF MICHIGAN, DESCRIBED BY A O. 

 CURRIER ON THE 112th AND 113th PAGES OF VOL. Ill, 

 JOURNAL OF CONCHOLOGY. 



BY JAMES LEWIS, M. D. 



Bulinus Tryoni, Currier. 



Several years ago I received from Mr. J. A. McNeil, of Grand 

 Rapids, Michigan, a large number of specimens of shells that I 

 have every reason to believe are identical with the slndls to 

 which the name Bulinus Tryoni has been given. The specimens 

 I received were of all ages ; and a considerable number were in 

 alcohol, with the soft parts intact. In my examination of these 

 specimens I could not discover that the few differences between 

 them and specimens of B. hypnoi'um from a great many differ- 

 ent localities were any greater or more remarkable than the dif- 

 ferences among the shells with which they were compared. The 

 principal difference was in the size of the largest adults — those 

 of Grand Rapids being unusually large. Some slight differences 

 in color were also apparent. But the?c differences and the dif- 

 ferences in size were less conspicuous than differences between 

 shells of the Atlantic States, and shells found in the prairie 

 regions. That these Michigan shells were to be regarded only as 

 an unusually fine development of the species hypnorum was also 

 suggested by peculiarities in other shells found near Grand 

 Rapids. Among the singular deviations from the usual typical 

 forms and colors, it may be unnecessary to mention more than 

 two — Helix alternata, Say, and Unio ligamentinus, Lam. 



Helix alternata (and most of the allied species) is usually 

 characterized by irregularly interrupted successions of brown 

 and white or light-yellowish patches over its whole surface — 

 alternations — a feature which probably induced Mr. Say to be- 

 stow upon the species the name " alternata." At Grand Rapids 

 this species varies from its usual habit as regards the ornamen- 

 tation of its surface, and also attains a somewhat unusually large 

 size. Specimens have been received from there of every degree 



