NATURAL SCIENCES OF PHILADELPHIA. 387 



the lateral angles, and each having a very prominent, compressed, central 

 node extending obliquely outwards and downwards, from which one or two 

 moderately prominent ridges pass down upon the basal plates. Second radials 

 between one-half and two-thirds as large as the first, distinctly convex, or 

 each rising into a small node ; about one-third wider than high, two of them 

 pentagonal, and three hexagonal. Third radials as wide as the second, but 

 rather shorter, three of them pentagonal and two heptagonal, supporting on 

 each of their superior sloping sides a slightly smaller secondary radial piece, 

 each of which is surmounted by two brachial pieces ; making, apparently, 

 twenty arms in the entire range. 



The first interradial pieces are about as large as the second radials, and like 

 them provided with a central node ; they are as long as wide, regularly hexa- 

 gonal, and support on their superior sloping sides two smaller pieces in the 

 second range, and two or three in the third, which connect on each side with 

 the secondary radial, and first brachial pieces. The first anal plate is nearly 

 as large as the first radials, as long as wide, hexagonal, and supports in the 

 second range, two rather smaller pieces, one of which is hexagonal, and the 

 other heptagonal ; above these there are two others, which connect with the 

 third radials, and secondary radial pieces on each side, and are surmounted 

 by two or three small, irregular pieces, which are flanked on either side by 

 the brachial pieces, and connect with those of the summit above. 



The vault is composed of irregular, moderately convex pieces, of various 

 forms, and provided with a subcentral proboscis, which rises abruptly from its 

 surface. 



Height from the base to the summit of the vault, - 66 inch ; do. to top of 

 third radials on the anterior side, 0-44. Breadth of base, 0'34 inch ; height 

 of do., 0*14 inch ; breadth across the summit, between the interradial spaces 

 on opposite sides, 0"61 inch. 



Locality and position. Cedar Creek, Warren County, Illinois. Burlington 

 Limestone, of the subcarboniferous series. 



Actinocrinps araneolus. Body small, much depressed, stelliform, nearly 

 equally convex above and below the arms, with deeply excavated interradial 

 spaces ; composed of smooth or obscurely granulose, convex plates, which are 

 strongly angular below the arms ; sutures moderately distinct. Base small, 

 fiat and subhexagonal ; columnar facet small, round, flat, and about one-third, 

 as wide as the base, pierced by a small central opening. First radial pieces on 

 a plane with the base, strongly convex, and angular in the middle, from which 

 a more or less angular ridge radiates to each of the sides, all slightly broader 

 than long, and hexagonal or heptagonal, the seventh angle at the middle of 

 the side connecting with the base being very obtuse. Second radial pieces 

 nearly as large as the first, wider than long, distinctly curved upwards at the 

 sides, and subangular along the middle ; presenting a hexagonal outline as 

 seen from below, but possessing an additional angle on each side, only seen in 

 a lateral view. Third radials of the same size as the second, from which they 

 extend horizontally outwards ; curving distinctly upwards on each side, and pen- 

 tagonal as seen from below, but each having one or two additional angles on 

 each side, where they connect with the superior arm pieces extending out from 

 the vault ; supporting on their superior, or more properly outer, sloping sides 

 apparently the first brachial pieces. 



The interradials are about two-thirds as large as the first radial pieces, a 

 little longer than wide, regularly hexagonal, and each support on their supe- 

 rior sloping sides two smaller pieces, which seem to belong more properly to 

 the vault, than the interradial series. 



The first anal plate is near two-thirds as large as the first radial, hexagonal, 

 and supports two smaller hexagonal pieces in the next range ; above these 

 there are four others in the third range, which connect with those of the vault 

 above, and with the superior arm pieces on each side. 



The summit is composed of small, somewhat irregular pieces, some of which 



I860.] 



