NATURAL SCIENCES OF PHILADELPHIA. 381 



slightly granulose plates. Base basin-shaped, expanding rapidly from its small 

 truncated columnar facet, considerably wider than high, and provided with 

 carinated sutures. First, radial plates large, about as high as wide, subquad- 

 rangular in outline, the two superior angles being rather distinctly truncated 

 for the reception of the interradial pieces ; all nearly, or quite as wide below as 

 above, and provided with a rounded sinus in the upper edge equal to about 

 half their own breadth, for the reception of the second radial pieces. Second 

 radials very small, triangular, about half as long as wide, and supporting en 

 their superior sloping sides, which are distinctly concave, the first divisions of 

 the arms. (Anal plates unknown). Interradial pieces comparatively large, 

 and each provided with a rather distinct central spine or tubercle. 



The arms are rather small, and above the first division on the second radial 

 piece, bifurcate again on the second piece, beyond which they appear to 

 be simple in most cases, though some of them present the appearance of sub- 

 dividing again on the second piece. Above the last bifurcation, they are at 

 first composed of a single series of joints, but gradually pass into a double al- 

 ternating series. All the joints below the bifurcations, and some of the larger 

 single ones above, are rather long, constricted around the middle, and provided 

 with a prominent projection on each side above. 



The column is compressed, twisted, and composed of nearly equal, rather short 

 segments, which are occasionally armed with short conical nodes or spines. 



Height from the base to the summit of the first radials, 0-43 inch ; breadth, 

 0-58 inch ; breadth of base, 0-45 inch ; height of do.. 015 inch. 



Locality and position, same as last. 



Genus DICHOCRINUS, Munster. 



Dichocrincs constkictus. Body small, oval subglobose, widest above, con- 

 stricted a little below the middle, and rounded or slightly truncate beneath ; 

 composed of thick plates, which appear to have been smooth, and are joined by 

 linear sutures. Base comparatively large, or forming about one-third the 

 entire length of the body, twice as wide as high, and more or less concave in 

 the middle below; each of its pieces having five obscure angles above, with 

 slight concavities between for the reception of the succeeding range of plates ; 

 columnar facet very small and round. First radial plates higher than wide, a 

 little unequal, having an oblong subquadrangular outliue, the two upper angles 

 of each being slightly truncated, apparently for the reception of very small 

 interradial pieces; one of them having a fifth obscure angle in the middle of 

 the under side. Sinus in the upper side of each first radial for the reception of 

 the second radials, rounded, and from one-third to one-half the breadth of these 

 plates. Anal piece slightly larger than the first radials, and having a subpenta- 

 gonal outline, narrowing upwards a little, and like the first radials, curving 

 inward above. (Other parts unknown.) 



Length, 0-39 inch ; breadth above the middle, 0-38 inch; do. at the constric- 

 tion below the middle, 032 inch; breadth of base, 0-33 inch; height of do., 

 0-14 inch. 



Locality and position. Bloomington, Indiana ; in beds probably equivalent to 

 the Warsaw Limestone, of the subcarboniferous series. 



Dichocrinds conus. Body large, obconical, longer than wide, composed of 

 thin, smooth plates, which are united by close fitting, linear sutures. Base 

 comparatively large, a little longer than wide, tapering regularly to the small 

 inferior extremity, which is slightly truncate ; both pieces subtrigonal in out- 

 line, though really hexagonal, if we count the slightly salient angles between 

 the shallow sinuosities in theupper margins ; columnar facet small, round ? and 

 provided with a small rim. Radial pieces large, longer than wide, presenting 

 an oblong outline, slightly wider above than at the base; all more or less con- 

 vex on the inferior margins, which in the anterior one, is provided with an 

 obtuse central angle ; sinus in the upper margin of each, about one-third as wide 



I860.] 



