INVERTEBRATES. 273 



sides being considerably longer than the lateral margins ; (the 

 other two unknown). First radial plates on the anterior side, 

 heptagonal, wider than long, the superior truncated edge being 

 longer than either of the others. Second radials smaller than 

 the first, hexagonal, and nearly twice as wide as long. Third 

 and fourth radials smaller than the second, wider than long, 

 and quadrangular or obscurely hexagonal in form, excepting in 

 one of the rays, where there are only four primary pieces, the 

 last of which is pentagonal (or obscurely heptagonal?), and 

 supports the secondary radials. In each of the other two rays 

 seen, there is a fifth radial piece, which appears to be pentago- 

 nal, and supports on its superior sloping sides the secondary 

 radial pieces. 



A remaining portion of a first interradial piece, in one of the 

 interradial spaces of our specimen, seems to have been penta- 

 gonal or hexagonal in form, and rests between the sloping sides 

 of two of the subradial plates, while it connects with a first 

 and second radial on each side. Anal pieces unknown. 



Arms, after the first division on the fourth and fifth radials, 

 rounded on the outside, and made up of pieces generally wider 

 than long ; one of them, seen in the specimen before us, appa- 

 rently bifurcating a second time on the sixth piece, and another 

 apparently on the eighth, beyond which they seem to be simple. 

 Minute intercalated semicircular pieces between each two of 

 the primary radials, as well as between the free arm pieces, 

 more or less distinctly developed. 



Column comparatively large, and tapering gradually from 

 the base, near which it is made up of extremely thin segments. 

 Central cavity, as seen in a transverse section, comparatively 

 large, and distinctly pentalobate. Height of body, to the top 

 of the first radial pieces, about 0.14 inch ; do. from column to 

 the top of the fifth radials, near 0.41 inch; breadth at the 

 summit of the first radials, 0.35 inch; breadth of base, about 

 0.16 inch. 



35 Sept. 14, 1S06. 



