NATURAL SCIENCES OF PHILADELPHIA. 161 



but its body is more spreading above and it has ten or more arms less, while 

 its vault is much more depressed and provided with a proboscis. It seems 

 to bear much the same relations to the section (b) of the genus Stroioc7-inus 

 that the subgenus Physetocrimts bears to the typical forms of Strotocrimts. 



Locality and posUion. Burlington Limestone of the Lower Carboniferous at 

 Quincy, Illinois. 



Subgenus PHYSETOCRLVUS, M. and W. 



Strotockinus (Physetocrinus ?) ASPER, M. and W. 



Body somewhat urn-shaped, being obconical below, with nearly straight, 

 gradually expanding sides, and rather ventricose vault. Base about ihree 

 times as wide as high, truncated below and angular, though not thickened or 

 properly expanded around the lower margin, which is so broadly and deeply 

 notched at the sutures as to present a trilobate appearance as seen from be- 

 neath. First radials wider than high, and as usual two heptagonal and three 

 hexagonal. Third radials of the same size as the second, and bearing on each 

 of their superior sloping sides a somewhat smaller secondary radial, each of 

 which bears on its outer sloping side a series of bracliial pieces, leading to 

 an arm, while on its inner sloping side it supports a small tertiary radial, 

 bearing on its inner side brachial pieces leading to an arm, and on its outer 

 a small quaternary radial, bearing on its outer side a brachial piece, and on 

 its inner another axillary piece, giving origin to two arms, thus making, as 

 far as can tie determined, ten arms to each ray, or fifty to the entire series. 



First anal piece as long as the first radials, but narrower, heptagonal in 

 form, and supporting one small piece over its middle and a larger one on each 

 upper sloping side in the second range; in the third range there are three, 

 in the fourth two pieces, and above these, three smaller pieces extending up 

 so as to connect with the vault. First interradial pieces of about the size of 

 the third radials, hexagonal in form, and bearing two smaller pieces in the 

 second range, above which there are some five or six very small, irregular 

 pieces, some of the upper of which extend up and connect with the vault. 



Vault rather ventricose, or more than one-third as high, near the middle, as 

 the body below the horizon of the arms ; composed of irregular nearly flat 

 pieces of moderate size ; opening apparently simple, at the highest point 

 atiout one-third of the distance from the middle towards the posterior side. 



All the body plates are protuberant and sharply angular in the middle, the 

 angular part, especially on the larger plates, forming a sharp transverse ridtje. 

 From the under side of this transverse ridge two or three others extend 

 downward on the first radial and first anal pieces, so as to connect with oth- 

 ers on the basal pieces. The second and third radial pieces have each about 

 three small pointed nodes, arranged transversely, while from the third radials 

 narrow ridges extend up to the secondary radials, thence up all the branches 

 to each arm base. All the smaller body plates also have a more or less pro- 

 jecting angular point in the middle. 



Notwithstanding the number of arms, the narrow anal and interradial 

 sinuses extend in so as to divide the disc quite in to the body, while even the 

 interbrachial sinuses extend nearly in to the body. The column is of mode- 

 rate thickness near the base, where it is round and composed of thin pieces 

 with shrirp projecting edges, pierced by a nearly round central canal. 



Height to horizon of arras, 73 inch ; breadth across at the interradial 

 sinuses, 0-90 inch ; height of vault, 046 inch. 



This species has its plates sculptured in nearly the same way, and present- 

 ing much the same roughened appearance seen in S. ffli/ptus, Hall (sp.), but 

 it differs materially from that and all of the othfr species known to us, that 

 resemble it in other respects, in having deep interradial and anal sinuses in 

 its disc, as in the subgenus Pht/xetocrinu's, with which it also appears to agree 

 in its ventricose vault. It is the only species known to us, however, appa- 



1869.] 11 



