548 PALAEONTOLOGY OF ILLINOIS. 



piece, and another piece resting on the latter. Above these, 

 others continue, up to connect with the base of the ventral 

 extension of the body. Arms unknown. Surface smooth. 

 Sutures not impressed. 



Breadth of body, 0.39 inch ; hight of same to top of first 

 radial, 0.17 inch; length of spines formed by the extension 

 of the second radial, 0.40 inch. 



In the peculiarity of having its second radial pieces developed into 

 long 1 , slender spines, this species agrees with Zeacrinux ! wiicrospinus, 

 McChesney, from the upper Coal Measures, and may be regarded as a 

 representative form of that curious Coal Measure species, in the upper 

 part of the Lower Carboniferous. It differs, however, from that species 

 specifically, not only in being much smaller and more delicate, but in 

 having its sub-radial pieces much shorter in proportion to their breadth, 

 and distinctly less produced and pointed at the ends. Its anal pieces 

 are also very differently arranged, the first or lower one being wedged 

 down obliquely under the first radial on the left instead of under that 

 on the right of the anal series, as in Z. mncrospinus. It is the first 

 American species of the Cyaihocrinidce we have ever seen with this 

 reversed arrangement of the anal series, though Prof. McCoY has rep- 

 resented a similar arrangement of these parts, in an aualagous form, 

 from the Carboniferous rocks of Scotland. Until the arms of this 

 crinoid can be seen, it is not possible to determine whether or not it 

 belongs to the genus Zeacrinus. 



Locality and position Pope county, Illinois ; Chester division of the 

 Lower Carboniferous series. 



ZEACRINUS STJB-TUMIDUS, Worthen Ms. 



PI. 21, Fig. 1. 



BODY depressed basin-shaped, about twice as wide as 

 , and composed of thick, massive plates. Base deeply 

 impressed for the reception of the column, which appar- 

 ently nearly filled the basal concavity, concealing the small 

 basal pieces. Sub-radials massive, strongly protuberant, 

 about as wide as long, and curving inward at their lower 

 extremities, to form the basal concavity, three hexagonal 

 and two on the anal side heptagonal. First radials about 



