28 PROCEEDINGS OF THE ACADEMY OF 



others continue on 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; height of same to top of first radials, 0.17 

 inch ; length of spines formed by the extension of the second radials, 0-40 

 inch. 



In the peculiarity of having its second radial pieces developed into long 

 slender spines, this species agrees with Zeacrinus(?) mucrospinus of McChes- 

 ney, 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, specifically, from Prof. McChesney's 

 species, not only in being much smaller and more delicate, but in having its 

 subradial pieces much shorter in proportion to 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. mucrospinus. It is the first American species of the Cyathocrinidie we have 

 ever seen with this reversed arrangement of the anal series, though Prof. 

 McCoy has represented a similar arrangement of these parts in an analogous 

 form from the Carboniferous rocks of Scotland. Until the arms of this cri- 

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

 properly to the genus Zeacrinus. 



Locality and position. Pope County, Illinois. Chester division of the Lower 

 Carboniferous. 



Zeacrinus (Hydreioxocrinus?) acanthophorus, M". and W. 



Body below the top of the first radial pieces much depressed, or nearly 

 saucer-sbaped, but concave below. Base very small and almost entirely hid- 

 den in the concavity of the under-side when the column is attached. Sub- 

 radial pieces small, four of them included in the concavity of the under side 

 and projecting horizontally outward into rather acute angles between the first 

 radials. so as to present a subtrigonal general outline, though they are really 

 hexagonal, their lateral and inner edges being connected with each other and 

 to the base, so as to form four very short sides with five obscure angles ; fifth 

 one larger than the others, proportionally longer, and curving upward at the 

 outer end, which is truncated so as to form a short side for the support of one 

 of the anal pieces. First radial pieces comparatively large, widening rapidly 

 from below to the top, which is truncated evenly the entire breadth, and 

 about twice a3 wide as the greatest height, all curving under to connect with 

 the subradials below in such a manner that the body rests upon them when 

 placed on a plane surface with the column removed. Second radials a little 

 smaller than the first, nearly twice as wide as long, pentagonal iu form, with 

 lateral margins short and not constricted ; each supporting two arms on its 

 superior sloping sides. Arms rather slender for a species of this genus, not 

 being wide enough to be in contact laterally all around when raised verti- 

 cally ; rounded on the dorsal side, rather rapidly tapering, and, so far as can 

 be seen in the typical specimen, all bifurcating on the second piece; below 

 the bifurcation the two pieces are each about as long as wide, the upper one 

 being sometimes slightly constricted around the middle ; arm piece above the 

 bifurcation rather slender, longer thau wide, rounded, and distinctly con- 

 stricted around the middle. 



First anal piece about twice as long as wide, and wedged so far down under 

 one side of one of the first radials. by the side of the largest subradial, as to 

 come nearly or quite in contact with the very small base. Second anal small 

 and resting upon the short upper end of the larger subradial, between the 

 upper part of the first anal on the right and the first radial on the left ; above 

 these the alternating series continues up to connect with the ventral ex- 

 tension. 



Ventral prolongation, or so-called proboscis, about equaling the apparent 



[April, 



