148 PROCEEDINGS OF THE ACADEMY OF 



Locality and position. Cincinnati Group of the Lower Silurian series ; 

 Kendall Co., Illinois. 



Heterocrinps subcrassus, M. & W. 



This species agrees so nearly with the last in most of its characters as to 

 render a detailed description unnecessary. It will be readily distinguished, 

 however, by its smaller size, as well as its less robust appearance, and the 

 different aspect of its arms. This latter difference consists in the more slender 

 appearance of all the divisions, and particularly in the joints of which they 

 are composed having their upper margins projecting beyond the base of each 

 succeeding piece above, so as to present a kind of upward imbricating appear- 

 ance and roughness, not seen in the arms of H. crassus. 



As in the last, its rays bifurcate first on the fifth and sixth pieces, and one 

 of them gives offabranch (?) on the leftside ofthe second radial, abovewhichit 

 bifurcates regularly on the sixth piece. After the first regular division on the 

 last radial piece, some of the arms are seen to divide again on the fourth, 

 others on the fifth, and others on the sixth pieces, after which one division is 

 known to bifurcate on the sixth piece, and still again on the thirteenth. 



Breadth of body at the summit of the first radial pieces, 0*27 inch ; height 

 of do., 0-13 inch ; length of rays from top of first radial pieces to the first 

 bifurcation, 0.21 inch ; entire length of arms from first division to extremities, 

 about 1-50 inches. Breadth of column at its connection with the base, - 15 

 inch. 



Locality and position. Cincinnati, Ohio. Cincinnati Group of Lower Silu- 

 rian . 



Heterocrine ? incurvus, M. & W. 

 Subgenus Anomalocrinus, M. & W. 



Body expanding rapidly from the base to the summit of the first and second 

 radial pieces, where it is more than twice as wide as high; composed of the 

 five basal, five first radial, and two second radial pieces. Basal pieces pen- 

 tagonal, of moderate size, wider than long, and forming together a low rapidly- 

 expanding, pentagonal cup. First radial pieces in three of the rays from 

 three to five times as large as the basal pieces, wider than long, two hexagonal 

 and one heptagonal, all with their superior lateral angles strongly incurved 

 between the arms, and each with a small protuberant, rounded facet above, 

 for the reception ofthe small succeeding radials. In the remaining two rays, 

 the first pieces are smaller and lower than those of the others, and each pen- 

 tagonal in form, with the upper side horizontally truncated its entire breadth, 

 for the reception of a larger second radial, which in these two rays agrees in 

 size and form, as well as in being included as a part of the walls of the body, 

 with the large first pieces of the other rays. Succeeding radials not more 

 than one-third as wide as those included in the walls of the cup, and forming 

 small, rounded, widely separated free arms, consisting of one to three quad- 

 rangular and one pentagonal pieces to each ray. Arms above the first bifur- 

 cation on the second or third pentagonal free radial, in two of the rays seen, 

 bifurcating again on the third piece, and, in one instance, sending off nearly 

 at right angles from the second piece after the first division, a strong tentacle, 

 or small lateral branch. 



First anal piece pentagonal, longer than wide, and resting between the left 

 sloping side of a large second primary radial and the right sloping side of a 

 first primary radial, with rather less than half its length projecting above the 

 focmer, and without extending down so as to bring its base in contact with 

 any of the other plates below. In the individual examined, this piece is 

 strongly incurved, and supports on its inner truncated end an oblong, narrow 

 second anal, which in its turn supports a smaller third piece, all of which are 

 arranged in a right line, and probably form one side of a proboscis. 



[Aug. 



