28 THE NAUTILUS. 
specimens are not fully matured. One of the two specimens has 
been presented to the “ Lea Collection,” inthe Academy of Natural 
Sciences of Philadelphia. 
ON A COLLECTION OF MOLLUSKS FROM GRAND TOWER, ILLINOIS. 
BY FRANK C. BAKER. 
During the latter part of April and first part of May, Mr. Frank 
M. Woodruff spent two weeks collecting birds in Jackson and Union 
Counties, Illinois, and incidentally picked up a number of mollusks, 
and the general conditions of the locality, and the small number of 
shells collected seem to warrant a few notes. ‘This locality is situa- 
ted on the Mississippi River, north of Big Muddy River, in the 
southwestern part of the State. 
Of the localites visited Mr. Woodruff says: ‘The shells were 
found in a rocky glen or cleft in the center of the chain of high 
precipices known by the names of Fountain Bluff, Devil’s Bake 
Oven and Backbone. This cleft or ravine begins about three-quar- 
ters of a mile from the face of the cliff and gradually descends in a 
northwesterly direction until the bottom is reached, and one may 
stand upon a broad shelf of rock ten feet from the ground, with 
high overhanging cliffs of bare rock on both sides. A stream of 
clear spring water flows down this ravine and falling over the high 
shelves of rock has formed numerous round pools or basins. I was 
surprised to find no shells in the stream, and could only collect a few 
specimens of Limnea humilis, which I found clinging to the wet 
moss under the falls. The balance of the shells were found under 
the moss and old logs at the base of the cliff’ Fountain Bluff is five 
miles from the town of Grand Tower, and is three miles long from 
north to south and about one and a half miles wide. According to 
Worthen’s Geology of Illinois, the Backbone or ridge is formed by 
an uplift of Devonian strata which is tilted to an angle of about 25°, 
and dips to the northeast. The bluffs consist of Chester limestone 
and sandstone overlaid by conglomerate. The top of the bluff is 
covered with a rich growth of timber, among which are Willow, 
Sweet Gum, Qupelo-tree, Sycamore, Cottonwood, Honey Locust, 
Hock Berry, Box Alder, Red Birch, White Ash, Black Ash, Red 
Oak, Mulberry, Persimmon, White and Black Oak, ete., are the 
most common.” 
