273 



The examples found in the thoroughfare and Lost Lake were of unusu- 

 ally large size; this is one of the few species of mussels which are 

 as large or larger in the lake than in the neighboring rivers. L. glans 

 appears to prefer shallow water along shore. A good number of shells 

 recently cleaned out by muskrats was found near the water's edge at 

 Long Point in the late autumn of 1913. 



In the Tippecanoe River at Belong this was a very abundant species 

 in the greasy whitish blue clay along shore, and was here one of the 

 favorite morsels of the muskrat. With the exception of Micromya 

 fabalis this is the smallest species of mussel found in the lake. It can 

 be easily recognized by its black epidermis, small size and purple nacre. 



8. Lampsilis iris (Lea). 



Rather common in the lake in shallow water near shore, found 

 scattered among the other species in the various shell-beds. There is a 

 good colony in the Lost Lake bed, and it is fairly abundant oif the 

 Depot grounds, by Kruetzberger's pier, at Long Point, and at the bed 

 near the mouth of Norris Inlet. 



The lake shells differ markedly from those of the neighboring rivers 

 so much that it is easy to separate the lake and river shells at a glance. 

 The lake shells are considerably more elongate, and the epidermis 's 

 stained a deep brown, mostly concealing the rays; when these are visible 

 they are brownish rather than green, and the umbones are rather eroded. 

 The shells, indeed, resemble somewhat the males of L. subrostrata, with 

 which they are associated. The lake shells exhibit a tendency to have 

 their posterior margin somewhat broader than the river shells, and the 

 shells are flatter at the posterior tip, becoming somewhat produced. 

 The river shells are more solid and heavy. 



Lampsilis iris is one of the few species of mussels which does not 

 show a marked decrease of size in the lake; indeed, some of the larger 

 lake examples run actually larger than those from the neighboring 

 rivers. Some of the largest lake shells examined have the following 

 dimensions : 



No. Length mm. Alt. mm. Diam. mm. 



1 69.6 37.3 21.0 



2 65.9 34.9 21.0 



3 68.0 34.6 22.0 



18—11994 



