280 Field Columbian Museum — [Geology,YVol. II. 



to be visible in a side view of the calyx, and the two large radials and 

 the inferradials are longer in proportion to their width, making the 

 calyx higher than wide. The rounder base is provided with a deep 

 basal cavity whose sides are subparallel. 



The natural casts are subcylindrical, moderately expanding to the 

 arm bases. The base is flat, having three slight protuberances which 

 give it a subtriangular appearance from below. 



The specimens here described appear to be more cup-shaped than 

 Miller's original figures indicate, and no mention is made by him of the 

 abrupt margin of the basal cavity. Examination of several hundred 

 specimens of this species, from the type locality, shows these features 

 to be characteristic and those which most easily distinguish this 

 species from P. gemmiformis. 



Locality: The specimens (Mus. No. P 8481), consisting of natural 

 molds and casts on which the above description is based, were collected 

 by the writer in the spoil heaps of the Chicago Drainage Canal near 

 Lemont, Illinois. A single incomplete individual from the clay pockets 

 at Romeo, Illinois, is doubtfully referred to this species. 



Pisocrinus quinquelobus Bather, Plate LXXXIV, Figures 5-7. 

 1893. P. quinquelobus Bather, Crinoidea of Gotland, Part I, p. 27. 



1895. P- milligani Miller & Gurley, Bull. 7 Ills. St. Mus. p. 8o, PL 



V, Figs. 27, 28. 



1896. P. quinquelobus Bather, Am. Geol., Vol. XVII, p. 184. 

 Bather's description is as follows: "Dorsal cup low; pentagonal 



as seen from ventral surface, the angles of the pentagon being radial in 

 position; the radial facets are very narrow, the radial processes corre- 

 spondingly broad, forming the concave sides of the pentagon ; basals 

 hidden in the concavity of the stem." To which may be added: surface 

 of plates smooth ; sutures very obscure, only visible with the aid of 

 a magnifier; stem round. The form and arrangement of the plates is 

 similar to the two preceding species. No plates of the ventral disc 

 present. 



The species is closely related to P. gorbyi S. A. M.,*but is distin- 

 guished from that species by its shorter cup and the position of the 

 basal plates, which in P. gorbyi are visible from a side view and in 

 this species are concealed in the basal cavity. 



Locality : f The species is represented in the collections of this 



Museum by four specimens, P 8414 and P 8827, which were collected 



by the writer in the clay pockets of the Niagaran limestone at Romeo, 



Illinois. These specimens are silicified and in a good state of preserva- 



* 17th Rept. Geol. Ind., p. 640, PI. VI, Figs. 17-20. 



