IOWA ACADEMY OF SCIENCES. 



113 



Exposure D. The shell stratum is not so rich in fossils as in C. Above it 

 tbere are fifteen or twenty feet of clay, in which a few Succineas were 

 found. In the clay below the shell stratum there are several distinct, 

 bu"- irregular, bands of lime nodules, — some vei'y large. 



Expofure E. Very similar to />, but with only one band of nodules. 



Expamre F. Fossils are vcy abundant in the shell stratum, which can 

 here be traced for three or four rods. The shell-less loess above is eight 

 or ten feet thick. 



Exp^'sures (V, H, I, -land K. These exposures were all formed from the same 

 ridge, by deep cutting and grading. The shell stratum is distinct in all 

 of them, and, as in all other sections, it follows in general the contour 

 of the surface. It varies in thickness here from six to twenty feet. It 

 is by no means equally fosslliferous throughout. 



Exposures L and 31. . Those were formed by the grading of High School 

 avenue. The street slopes westward from the high school, and drops 

 about sixty feet in a block. On the north side tlie shell stratum is 

 nearly parallel to the street grade, and but little above it. On the 

 south side it dips b -low the street about half-way down the slope. 



Exposures N, O, P, Q. B, S and T These are all exposures along the road 

 which winds eastward from the Tenth avenue entrance to Fairmount 

 park At N the road is about 1J"5 feet above the river valley, and the 

 shell stratum (which is here very rich in fossils), extends about three 

 feet higher. It dips down toward the west at such an angle that it 

 would connect with the shell stratum at E, which is about 100 feet 

 lower. 'J he same layer may be traced, more or less indistinctly, to O, 

 where there is a cut about twenty feet deep. The shell stratum rises 

 to abour eight feet above the roadbed (here about 200 feet above the 

 river valley), but fossils are not abundant. The remaining exposures 

 along this road are formed by the road cutting ti-e smaller lateral lobes 

 of the greater ridges. The letters apply to the extent of road from 

 bend to bend, not to individual exposures. At the southern bends in 

 the road are the high points, the road sloping down to near the bases of 

 the ridges to the north. Fossils are found ia most of the little expos- 

 ures (which, in but few cases, exceed fifteen feet in height) along the 

 road, but they are nowhere as abundant as in some of the exposures 

 along the bluff fronts. The exposures which are represented on the 

 map, but not lettered, are non- fosslliferous. 



THE IOWA LIVERWORTS. 



BY B. SHIMEK. 



Among the groups of plants hitherto neglected by Iowa 

 botanists, the liverwot-ts are by no means the least interesting. 

 A few of the large thalloid species have long been familiar 

 objects to botanists working in ottier fields, but the general 

 lack of economic importance of the group, and the habits and 

 small size of most of the species, no doubt account for the fact 

 that they have attracted less attention than they deserve. 



In general, the liverworts prefer moist places. They may 



