•22S 



Cincinnati Society of Natural History. 



Column. — The column is round, smooth, very gently expanding to 

 unite with the calyx, and seems to have tapered to a point at no great 

 distance from the calyx, after throwing off numerous floating 

 rootlets. This latter supposition is based upon the two facts, that th e 

 column, over an inch in length, attached t.> a head, has materially 

 diminished in size, and upon the same slab, near Iry, there occurs a 

 yet smaller tapering column throwing off small rootlets, at irregular 

 distances from each other, which are about the size of what we may 

 suppose pinnules would be in a species in this genus of the size of the 

 one under consideration. The length of these little rootlets is about 

 one fourth of an inch, and the length of the fragment of the column so 

 preserved is about one and a hall inches. The plates are of nearly 

 uniform thickness. 



Body. — The calyx is like a smooth, reversed, truncated, slowly taper- 

 ing cone, having a length more than one and a half times its greatest 

 diameter. The basal plates are pentagonal, higher than wide, the two 

 uniting sides being the longer, and the two upper sloping sides being 

 the shorter ones. The subradials are hexagonal, longer than wide, the 

 upper sloping sides being a little longer than the under ones. The 

 first radials are pentagonal, longer than wide, and the upper or articu- 

 lating surface is truncated the entire width for the support of the 



brachials. 



Brachials. — There are four brachials or free radial plates supporting 

 arms in each of the five series. These are round or subcyclindrical on 

 the outer face, tapering very slightly only, up to the middle of the 

 fourth plate, where there is a little expansion." at the lower part of the 

 sloping sides, which support the arms. The first plate is the longer 

 one, but they decrease in length, very slowly, so that the fourth plate 

 is fully two thirds as long as the first one. 



Arms. — The arms are remarkable in their manner of division. Every 

 third plate from the last brachial throws off an armlet or little arm, 

 which occurs in every instance observed, and is shown upon three 

 arms on one specimen to the sixth bifurcation. The armlets do not 

 possess the character of pinnules, but in no instance do they bifur- 

 cate. This character is quite well shown in the magnified view of 

 part of two arms shown in fig. 5a. There are ten specimens of this 

 species on a large slab, more or less perfect, and one of them 

 shows part of eight arms, another part of six, and two others 

 each preserve a considerable part of four, and others have some in a 

 greater or less state of preservation. From an examination of these 



