iUM t m^ 



NOTES ON A COLLECTION OF MOLLUSKS FROM 

 THE VICINITY OF ALPENA, MICHIGAN.* 



Frank Collins Baker. 



Some twenty-five years ago Dr. William A. Nason, of Al- 

 gonquin, Illinois, made a large and somewhat exhaustive col- 

 lection of the Mollusca which inhabit the vicinity of Alpena, 

 Michigan. Unlike many collectors of that day (and later 

 days, too, for that matter) he kept the different localities 

 separate and preserved much interesting and valuable data. 

 Dr. Nason has very kindly allowed the writer to make a care- 

 ful study of the collection and on account of its completeness 

 and exactness it has been thouo^ht that a catalogue of the col- 

 lection, with notes, would be of considerable value to those 

 who might have occasion to work up material from this 

 region which might not be as abundant as the material now 

 in hand. 



Of the 48 species and varieties in the collection, 9 are 

 land shells and 39 are fluviatile forms. This shows a very 

 large preponderence of fluviatile over terrestrial species. 

 The fresh water pulmonates comprise 75 per cent. (26 species 

 and varieties) of the fluviatile forms; Lymnaea is represented 

 by 10 and Physa by 8 species and varieties. The bivalves 

 seem to be few in number, both as to species and individuals, 

 and the tenobranchiates (Goniobasis, Amnicola, etc.) are 

 but poorly represented. There are many interesting varia- 

 tions among the L^'mnaeas and Fhysas, these variations being 

 due, in part at least, to the various environments in which 

 the different colonies lived. 



The locality is situated in an interesting part of the 

 country, the northern lakes, Superior and Huron, seeming to 

 form particularly favorable environments for producing pecu- 

 liar and characteristic forms of mollusks. The heavy, light- 



* Presented by title to the Academy of Science of St. Louis, Jan. 15, 1906. 



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