NEW CRINOIDS FROM THE CHICAGO AREA. 



BY ARTHUR WARE SLOCOM 



In the fall of 1905 the attention of the writer was called to the fact 

 that fossils were being found at a quarry operated by the Illinois Steel 

 Company for limestone for flux, at Romeo, Illinois. Upon visiting the 

 quarry it was found that not only was the limestone itself fossilf erous, 

 but that silicified fossils were abundant near the bottom of large 

 clay pockets which were exposed at various places in the quarry. 

 These clay pockets occupy large, irregular shaped cavities in the lime- 

 stone. The larger ones are 1 5 or more feet deep and their width is 

 often greater than their depth. In some instances several are connected, 

 their connections following the jointing of the limestone. These 

 cavities, or "pot-holes" as they are sometimes called, often associated 

 with furrows, are to be seen in many places along the Chicago Drainage 

 Canal where the surface of the rock is exposed. The cavities vary in 

 size from a fraction of an inch in depth to those mentioned above. 

 These cavities or pot-holes must have been in part subjected to the 

 action of running water since their sides are smooth. They are fre- 

 quently broader at the base than above and may even be cone-shaped, 

 with the apex of the cone above. Their filling is for the most part 

 a blue homogeneous clay. This contains small silicified fossils of Niag- 

 aran age, small, modern, fresh-water shells and fragments of pyritized 

 and charred wood. No large boulders or pebbles occur in the clay, 

 although these frequently form a capping of the pockets. The question 

 of the origin of the filling of the pockets is a matter of no little interest. 

 The clay could not be of preglacial origin because of its content of 

 wood and modern shells. If of postglacial origin, the presence of 

 the Niagaran fossils is difficult to account for. A wall of the quarry 

 showing typical pockets is represented in Plate LXXXII. A single 

 one in more detail is represented in Plate LXXXIII. 



During the fall of 1905 and the spring and summer of the following 

 year, over 400 fossils representing 38 species were collected by the 

 writer from these clay pockets. These fossils were divided as follows: 



Corals 293 specimens, 1 5 species ; 



Sponges , . 20 specimens, 3 species; 



Bryozoans 12 specimens, 4. species; 



273 



