FOSSILS OF THE CHESTER GROUP. - 555 



cutly not always extending up far enough to have its upper 

 angle truncated by one of the succeeding anals above. 

 Second anal piece considerably smaller than the first, and 

 resting upon the upper truncated side of one of the sub- 

 radials; above these two or three smaller pieces appear be- 

 tween the arms. Surface smooth. Sutures between the 

 body plates rather deep. Arms slightly convex on the 

 outer side, with lateral margins flattened and straight, so 

 as to fit closely together when raised up vertically; each 

 composed below of a single range of wedge-formed pieces, 

 but soon passing into a double alternating series above. 



Breadth of body across the middle, 0.90 inch; do. across 

 the second radials, 0.64 inch; hight to top of first radial 

 pieces, 0.40 inch. 



This is a very neat, symmetrical crinoid, unlike any other known to 

 us, and remarkable for having its much depressed body rounding in 

 above, at the top of the first radial pieces, so as to be very distinctly nar- 

 rower across above the top of the first radials than below. Its sides also 

 round very neatly under below, and so far into the deep concavity of the 

 under side that the lower ( inner ) ends of the subradial pieces curve 

 upward into the mesial concavity nearly as far up as their outer or 

 upper ends. It seems to be the same form figured by YAJSDELL and 

 SHTOIARD, in their " Contributions to the Geology of Kentucky ; " (see 

 their fig. 4, , &, without a description or name,) from near Grayson 



Springs, Kentucky. 



The specific name is given in honor of Dr. BOYD, of Chicago, to whom 

 we are indebted for the specimen described. 



Locality and position Chester, Illinois; Chester division of the Low- 

 er Carboniferous series. 



GENUS PLATYCKQttTES. 

 PLATYCRINITES PARVULUS, M. and W. 



PI. 20, Fig. 7. 

 Platycrin 1 pareulun, MEKK and WORTHEX, 1865. Proceed. Acad. Natural Sci., Phila., p. 163. 



BODY very small, short, sub-cylindrical, or deeply cup- 

 shaped. Base depressed basin-shaped, or several times as 



