62 Lake Maxinkuckee, Physical and Biological Survey 



somewhat the males of L. subrostrata, with which they are asso- 

 ciated. The lake shells exhibit a tendency to have their posterior 

 margin somewhat broader than that of 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 



2 65.9 34.9 21 



3 68.0 34.6 22 



4 64.9 35.8 22.7 



5 67.0 36.8 20.9 



6 67.7 33.8 21.5 



No young shells were found, even the smallest appear rather 

 old. The smallest three measure : 



Length mm. Alt. mm. Diam. mm. 

 41.4 21.2 12.5 



38.9 21.5 12.5 



37.0 20.0 12.3 



For comparison with the lake shells, the dimensions are given 

 of the largest two shells found in Yellow River : 



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



1 67.0 34.5 22.9 



2 64.0 33.5 21.0 



Only one gravid example was found ; this was obtained at Lost 

 Lake bed Sept. 7, 1908. 



Of all the species of mussels in the lake, L. iris has the best 

 connection, through scattered individuals along the Outlet, with the 

 shells of the Tippecanoe River, a few shells having been found 

 almost through the whole length of the Outlet. The outlet shells, 

 like those of the rivers, are brightly rayed. The species is abund- 

 ant in the Tippecanoe River at Belong. A number of examples 

 were noted in spawning condition there in late August and early 

 September in 1908. Observations in the Maumee River would in- 

 dicate that these species, L. parva and L. midtiradiata, do not have 

 exactly the same breeding season as many other species of Lamp- 

 silis (luteola, recta, ligamentina, etc.) but are sometimes fertilized 

 in July, spawning in August and September. Being small and 



