Lake Maxinkiickee, Physical and Biological Survey 



69 



Most of these shells blistered posteriorly. 



The males are fairly like those of river; the females are more fanshaped. Weight of the 10 shells, 15 oz.; 

 only a few are rayed. 



12. POCKETBOOK 



LAMPSILIS VENTRICOSA (Barnes) 



Rather common at the Long Point mussel bed; a few found 

 in the bed by Farrar's and a few in Lost Lake. The species as 

 found in the lake is markedly dwarfed and quite different in ap- 

 pearance from the usual river form. There are two types in the 

 Long Point bed. One consisting of females, having the post 

 basal inflation of the shell characteristic of that sex, not exactly 

 as in the river form, however, but somewhat more restricted ; this 

 feature, along with a peculiar stain of the epidermis which con- 

 ceals the normal coloring of the shell, causes them to very closely 

 resemble a short female L. luteola. The other type, an oval shell 

 without the post-basal inflation, was at first taken to represent the 

 males, but some of them were found to contain glochidia. These, 

 too, bear a marked resem.blance to L. luteola, and the only way to 

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

 examination of the umbonal sculpture. This in ventricosa con- 

 sists of 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 neighboring lakes with which to compare 

 them. In some of the small lakes of Michigan where Dr. Robert 

 E. Coker collected, he experienced a similar difficulty in dis- 

 tinguishing L. ventricosa and L. luteola. He sent sets of criti- 



