MUSSEL FAUNA OF MAUMEE RIVER. 



5 



as "the prairie." A careful examination of this ditch revealed no 

 mussels at all, and it is not likely they could live in the mucky 

 bottom, though it is possible that glochidia might be carried through 

 the stream by migrating fishes. 



During the glacial period the entire region was buried under the 

 ice, and every form of molluscan life was exterminated. At the 

 melting of the ice sheet great bodies of water were formed which 

 could find no outlet to the eastward on account of the still unmelted 

 ice, and therefore all the water was compelled to drain toward the 

 south and west into the Ohio and Mississippi Valleys. The old 

 channels can still be traced and are represented on the geological 

 maps of the region. The geologists tell us that at first there were 

 two of these lakes entirely separated from each other. The eastern- 

 most one, Lake Maumee, covered the present basin of the Maumee 

 Eiver and the upper part of the Wabash Basin and was 100 feet 

 higher than Lake Chicago, which lay to the west. Lake Maumee 

 drained through the Maumee and Wabash Valleys into the Ohio, 

 while Lake Chicago found an outlet along the Des Plaines and 

 Illinois River Valleys. 



The restocking of the region with mussels must have been effected 

 by migration through these respective outlets. At this period sev- 

 eral of the more hardy species came up through the Wabash Basin 

 into Lake Maumee, as is attested by the finding of their shells among 

 the fossils of the period. At the beginning, therefore, the Maumee 

 Basin was restocked with Ohio Valley species of mussels, which came 

 to it by way of the Wabash River.^^ 



After the ice had retreated far enough northward to reveal the 

 surface features of the region under discussion, it exposed the valley 

 of an ancient preglacial river, sometimes called the Huronian River, 

 and now known as the Saginaw-Grand Valley. This river valley 

 runs east and west across the southern part of the State of Michigan 

 and became a channel connecting the two lakes just mentioned. The 

 opening of this channel gradually lowered the water in Lake 

 Maumee to the level of that in Lake Chicago. A series of terminal 

 moraines which had formed along the southern margin of Lake 

 Maumee were enabled by this lowering of the water to assert them- 

 selves and close the Wabash outlet. These moraines are known to 

 geologists as the Mississinewa Moraine, to the south and west of 

 which lies the Mississinewa River, the Salamonie Moraine, to the 

 north and east of the Salamonie River, the Wabash Moraine to the 

 north and east of the main branch of the Wabash River, the St. 

 Joseph- St. Marys Moraine to the east of those two rivers, both of 

 which drained originally into the Wabash, and the Defiance Moraine 



" For an interesting discussion of this subject, see Simpson, American Naturalist, vol. 

 XXX, p. 379-384. 



