344 PROCEEDINGS OF THE ACADEMY OF 



umn, to the top of the base, and still more rapidly from there to the top of the 

 first radials, so as to make the breadth at the latter point about twice the 

 height. Base forming less than half the height of the body, somewhat basin- 

 shaped, though narrow below, or ornamented with small irregular wart-like 

 nodes, which show some tendency to form three or four vertical rows, or ridges 

 on each basal piece. First radial pieces comparatively large, somewhat oblong 

 in form, being longer than wide, with the widest end above, all convex along 

 up the middle, and strongly beveled, or excavated along the sutures on each 

 side, — while the surface of each is ornamented with small, irregular, wart-like 

 nodes, similar to those on the base ; these sometimes coalesce into irregular 

 ridges, but are usually arranged in three rows, starting from the most promi- 

 nent upper end of the plates, and radiating to the base ; facet for the reception 

 of the second radial pieces about one-third the breadth of the upper end of the 

 plates, and somewhat excavated. Anal piece of much the same size, and 

 general nodose appearance as the first radial on each side, but somewhat longer, 

 and having an irregular hexagonal form. Second radial pieces small, about 

 twice as wide as long, and more or less quadrangular in form. Third radials 

 slightly larger than the second, with a pentagonal form, the upper sloping 

 sides supporting the first division of the arms. 



Arms rounded, composed at first of pieces about as long as wide, upon the 

 second or third of wliich they bifurcate, the outer divisions remaining simple, 

 and the inner ones bifurcating again on the second or third piece, the outer 

 division, as before, remaining simple, and the inner bifurcating a third time on 

 the second pieces, thus making in the posterior rays (the only ones seen) eight 

 arms to each ray, or forty in the whole series, if other rays have the same num- 

 ber. All the simple arms are long, slender, rounded, and but slightly tapering ; 

 near their bases they are each composed of a single series of somewhat wedge- 

 formed pieces, but gradually pass into a double series of minute interlocking 

 pieces. 



Breadth of body, 0-98 inch ; height about 0-43 inch. Length of one of the 

 simple arms, about 1-fciO inches; thickness of same at base, 0-05 inch. 



Associated with the specimen from which the foregoing description was 

 drawn up, several other imperfect examples were found, differing more or less 

 in form and in the arrangement of their ornamentation, which either indicate 

 considerable variations in these characters, or the existence of several allied 

 species. One of these has the first radial and anal plates more abruptly spread- 

 ing, and proportionally wider than in the typical form, while its nodes are more 

 coalescent, so as more generally to run into continuous ribs. On the base, for 

 instance, each of the two plates has three somewhat nodulous vertical ridges, 

 with intervening rows of the little nodes, while the three rows of nodes on the 

 first radial and anal pieces often run together so as to form mere nodulous 

 ridges. It is possible this would be found to be a distinct species, if we could 

 examine a specimen showing the arms. If so, it may be called D. stelliformis, 

 in allusion to the star-like appearance produced by its spreading first radial 

 pieces, with their little ridges running outward and converging to the outer 

 extremity of each. 



In another individual the nodes and ridges are all nearly obsolete, excepting 

 a few of the former, which are very prominent at the middle of the outer ends 

 of the first radials; while another has a single prominent node near the small 

 facet in each first radial, for the reception of the second, with a few irregularly 

 scattering nodes on other parts, and slender, obscure, nodular ridges near the 

 lateral margins. From the general appearance of these specimens, we are 

 rather inclined to the opinion that they are all varieties of one variable species. 

 Locality and position. — Same as last. 



Genus DORYORINUS, Roemer. 

 In the second volume of the Reports of the Geological Survey of Illinois, we 

 distinctly recognized the Dorycrinus group as forming a well-defined genus, 



[Dec. 



