2 Trans. Acad. Sci. of St. Louis. 



horn colored shells seem characteristic of these northern 

 waters. 



Dr. Nason has furnished the following notes on the 

 particular habitats or environments where shells were col- 

 lected. " Thunder Bay Island is one mile east of the north 

 point of Thunder Bay. Here I found the shells in pools of 

 water in ledges of limestone which are accessible to the waves 

 of the lakes durino; storms or high water. Sugar Island is a 

 low island between Thunder Bay Island and the main land, a 

 little to the north. Following westwardly the north shore of 

 Thunder Bay, Whitetish Point is about half way to the city 

 of Alpena. Isaacson's farm includes a small creek which 

 empties into Thunder Bay between Whitefish Point and the 

 city of Alpena, about one mile inland. Thunder Bay River 

 (Ox Bow) is about two miles from the mouth of the river, 

 northwest of the city. Stony Point is about two miles south 

 of the mouth of the river on the shore of the bay and is a low 

 limestone beach. 



" Sulphur Island is a small, low island near the southern 

 point of Thunder Bay, about eight miles from the city of 

 Alpena. Long Lake is about twelve or fifteen miles north of 

 Alpena and its shores are mainly limestone rocks and low 

 bluffs, except at the outlet of the creek which flows into 

 Thunder Bay River. The shells were mainly collected on a 

 broad, sandy beach about the outlet, and in from six inches 

 to a foot of water. 



" The change of localities gave the shells a difference in 

 development which is very interesting. The contrast between 

 the solid forms of Thunder Bay Island, where the waves and 

 cool water of Lake Huron was almost daily forced into the 

 pools where the shells developed ; and the still, swampy pool 

 where the Sugar Island Lymnaeas lived, where the shores 

 were low, but protected from the rough storms of the lake, 

 give a hint of conditions very interesting, biologically." 



The collection bears out all that Dr. Nason has said con- 

 cerning the biologic features, and a study of the material 

 from a biometric standpoint would undoubtedly yield some 

 very interesting results. 



