282 



to distinguish the two species, as they occur in the lake, was by an 

 examination of the umbonal sculpture. This in ventricosa consists of a 

 a few coarse parallel ridges; in luteola the sculpture is of numerous fine 

 wavy lines. 



The lake L. ventricosa was so markedly different from the species 

 as usually known that it was compared with a large series of both lake 

 and river forms. Of river shells only a few from the central part of 

 the Maumee, where for some reason the shells are markedly dwarfed, 

 bore any close resemblance to it. None was found in any of the neigh- 

 boring lakes with which to compare them. In some of the small lakes 

 of Michigan where Dr. Robert E. Coker had collected he had experienced 

 a similar difficulty in distinguishing between L. ventricosa and L. luteola 

 and had sent sets of critical specimens to Mr. Bryant Walker of Detroit, 

 Mich., who identified the shells with a few coarse straight undulations 

 on the beaks as Lampsilis ventricosa canadensis and the others as L. 

 luteola. 



The Maxinkuckee specimens were also compared with L. ventricosa 

 from Lake Champlain, and were found to be much like them. The 

 Champlain examples which were free from staining of the epideimis 

 more closely resembled in color the ventricosa of the rivers. 



The specimens of L. ventricosa differed considerably in the different 

 beds. Lost Lake examples are usually rather small, and are stained a 

 peculiar ashy-gray. Those from the beds near Farrar's are mostly 

 small and apparently young and are rather well rayed; they resemble 

 river forms more closely than any others in the lake. 



The large oval L. ventricosa of Long Point are the heaviest shells 

 of the lake. A peculiarity of several of these shells is a conspicuous 

 rib-like thickening on the inside, extending from near the umbonal cavity 

 postero-ventrally. The nacre is soft satiny in lu.ster, and not very 

 iridescent. This oval form of ventricosa found at Long Point furnishes 

 the only shell in the lake that could be used to any advantage in the 

 manufacture of buttons, and even it produces rather inferior material. 

 Some of these shells were sent away to a button factory at Davenjjort 

 and buttons were made of them. The following is a set of measureme^.ts 

 of these large shells: 



