660 THE AMERICAN NATURALIST. [Vor. XXXV. 
The geography of the river from South Park to the lake 
may be thus described: From south of Genesee Park to 
within a short distance of a small dam it is broad, deep on 
one side and affording a shelving, shallow bank on the 
other, the bottom being composed of a clayey mud. Unios, 
Campelomz, Goniobases, Sphzria, and Physz are here very 
common. Just before reaching the dam the river shallows 
very perceptibly, flowing rapidly over great ledges of lime- 
stone. Lampsilis luteolus and L. iris are very common 
here, and also Goniobasis, while Physa is not quite so 
common. 
Below the dam, which is now broken and very much out of 
repair, the river flows rapidly over a rocky bed, in many places 
the water being so shallow that persons can wade across. The 
right bank is very rocky, more so than the left, and forms little 
sheltered bays here and there, in which Goniobasis and Physa 
live by thousands, the former making a veritable pavement in 
some places. Lampsilis luteolus is also common, although 
apparently preferring the middle of the river. Along the 
bank here the Unios lie in great windrows, their dead shells 
piled up like the débris on an ocean shore. In this pile of 
shells such species as Lampsilis iris, L. luteolus, Quadrula 
rubiginosa, Lampsilis complanatus, and Alasmodonta rugosa are 
common. The water near the rocky shore also affords good 
retreats for the mollusks. 
Near the Erie Railroad bridge the water deepens, and the 
Unios begin to thin out, although Lampsilis /uteolus seems to 
be as common as ever. Goniobasis also flourishes, while Physa 
almost dies out. Near Clarissa Street bridge the water 
becomes still deeper, and the only species found are Lam- 
psilis luteolus, L. iris, L. complanatus, and Goniobasis, with à 
stray Campeloma or Spherium. - Physa seems to have disap- 
peared completely. Below Clarissa Street bridge the water 
deepens to the state dam, beyond which it is very shallow and 
rocky, so far as known affording no mollusks save an occa 
sional Goniobasis or Campeloma. At the dam the water 1s 
deflected in a large stream for factory uses and again reaches 
the river at the first falls. 
