158 PROCEEDINGS OP THE ACADEMY OF 



posed of alternately thicker and thinner pieces. Surface apparently smooth 

 Sutures slightly furrowed excepting those between the first and second radial 

 pieces, which are distinctly gaping when the arms are folded together. 



Height of body to the top of the first radial pieces, 0-25 inch; breadth of do. 

 0-48 inch. Length of arms above the second radials, 1-90 inches or more; 

 diameter of column at its connection with the base, 0-13 inch. 



This species seems to be closely related to S. decabrachiatus, Hall, (Iowa 

 Report, p. 679, pi. xxv. fig. 1,) but is larger and more robust, and its second 

 radial pieces differ materially in form, being nearly or quite twice as wide as 

 long, while in S. decabrachiatus they are ''nearly once and a half as long as 

 wide." Its basal pieces are also proportionally about twice as large. Other 

 differences would doubtless be apparent, if we had the means of comparing all 

 the corresponding parts of each with those of the other. 



Locality and position. Bay City, Pope Co., Illinois. Chester division of the 

 Subcarboniferous limestone series. 



POTERIOCRINDS (SCAPHIOCRINUS) ? NoRWOODI, M. & W. 



Body small, depressed basin-shaped, rounded and concave below, breadth 

 three times as great as the height to summit of first radial pieces. Basal pieces 

 very small, deeply impressed within the concavity of the under side, and almost 

 entirely hidden by the column. Subradial pieces comparatively well developed, 

 curving under to connect with the concave base ; three pentagonal, (exclusive 

 of. the scarcely-defined angle at the middle below,) and two on the anal side 

 hexagonal. First radial pieces short, and about twice as wide as high, pen- 

 tagonal, with the upper side transversely truncated its entire breadth. Second 

 radials as wide as the first, and twice as long, pentagonal, and at the middle 

 above acutely angular. Arms after the first division on the second radial 

 bifurcating at least once more, on the third or fourth piece, the joints beyond 

 being slightly longer than wide, and supporting alternately on opposite sides 

 of the arms strong, long-jointed, rather remotely-separated tentacles. First 

 anal piece nearly as large as one of the subradials, pentagonal, and resting 

 between the upper sloping sides of two of the subradials, with its right superior 

 sloping side supporting the left under side of a first radial, and its left upper 

 side a third anal piece, while its short left vertical side connects with the 

 second anal piece. Second anal about the size of the first, and resting upon 

 the short upper truncated side of one of the subradials, with its left side con- 

 necting with one of the first radials, and its right with another anal piece. 

 Above these several other anal pieces are seen to rise so as to form apparently 

 a narrow, rounded, lateral proboscis, on a range with the arms, which it ap- 

 pears to scarcely exceed in thickness. Summit and column unknown. 



Surface nearly or quite smooth, excepting an angular ridge or carina, which 

 extends up each second radial its entire length. Sutures distinct and indented 

 a little at the connections of the corners of the first radials and the subradial 

 pieces ; that between the first and second anal pieces gaping. 



Height to summit of first radial pieces, 005 inch; breadth, 0-15 inch. 



This little species presents rather a combination of characters belo"ging to 

 several groups. In the number and arrangement of its anal pieces forming 

 a part of the walls, as well as in the general structure of its body, it agrees 

 with Poteriocrinus, and its depressed form and round deeply-concave underside 

 are characters belonging to the group Zeacrinus, while the form of its arms, 

 and the distinctly gaping character of the sutures between its first and second 

 radial pieces, suggest relations to Scaphiocrinus. Its apparently distinctly 

 lateral, slender, rounded proboscis, however, would remove it entirely from 

 the genus Poteriocrinus to Cyathocrinus. Indeed if we could be sure the 

 latter character is real, and not produced by the accidental folding together 

 into a cylindrical form of merely a part of the external wall of the large trunk 

 bo characteristic of the genus Poteriocrinus, we would not hesitate to call 



[Auj 



g- 



