286 The American Geologist. May, 1895 
subulare, P. elevatnm, and perhaps P. jxtllidiim; Valvata sin- 
cera; SpIuBrium strialinum\ U^iio phaseohoi, U. clavus, ZT. 2JUS- 
tulosus, and its var. Schoolcraft i, U. occidens (?), U. luteolus, 
U. undulatus, U. rectus, U. trigouus, and U. solidus. All the 
species are still living, but at least three of the Unios and one 
Pleurocera appear to be now restricted to waters tributary to 
the Mississippi and are not known in the present fauna of the 
St, Lawrence drainage area. The three trees whose drift- 
wood occurs in the same laj^er with these shells, are identified 
by Prof. D. P. Penhallow of McGill University, Montreal, as 
probably Fraxiims qiiadrangulata, Quercus ohtusiloha, and 
Taxus baccafa, var. canadensis. The first and second are 
common now in portions of southern Ontario, but not farther 
northward, while the third occurs throughout the greater part 
of Canada. The section supplying these fossils includes the 
following beds in descending order: 
Feet 
Sandy soil, followed by brownish gray clay with boulders 3 
Stratified bluish gray calcareous clay (making buff-colored brick) 69 
Brownish or drab clay, much jointed (making red brick) 11 
Brownish yellow stratified sand 4 
Blue calcareous clay, with peaty flakes 3 
Brown sand and gravel, showing false bedding, with thin layers of blue or 
brown clay— lossiliferous 18 
Blue boulder-clay (till) with striated boulders 3 
Hudson River shales, quarried to make dark red pressed brick 30 
Total : 141 
The base of the section is at the level of the river, which is 
nearly that of lake Ontario, 247 feet above the sea. Immedi- 
ately above the lower boulder-clay, at a height of 280 to 298 
feet above the present sea level, the fossil shells and wood 
were found ; and evidently the Unios in the lower part, rest- 
ing directly on the till, occupy the place where they were liv- 
ing, since the}^ have not been waterworn, but retain their 
dark epidermis, and often have the two valves united. 
These observations are believed by the present writer to 
show that the ice-dammed lake Iroquois, the Late Glacial or 
Champlain representative of lake Ontario, stood first, when 
drainage was obstructed b}'^ the ice-sheeet at boundary 5, 
plate X, at a level not more than 30 or 40 feet above the pres- 
ent lake. There next ensued, probably, a gradual rise of the 
lake, due to an uplifting of the country about its outlet at 
Rome, in central New York, flowing to the Mohawk and Hud- 
