NATURAL SCIENCES OF PHILADELPHIA. 25 



traded above. Basal plates of moderate size, pentagonal in form, and 

 out horizontally so as to form a nearly flat pentagonal disc, excepting that the 

 salient angles are curved upward a little; facet for the attachment ol the 

 column small, compared with the size of the base, round and no1 impressed 

 Subradial plates large, forming the widest part of the body, convex, on the 

 outside, but not from thickening; about as wide as long, hexagonal, with 

 perhaps the exception of one on the anal side of heptagonal form ; all curving 

 under below to connect with the base. First radials somewhat smaller than 

 the subradials, wider than long, pentagonal in form, and provided above with 

 very small, shallow sinuses for the reception of the second, which arc small, 

 but more thau filling the shallow little sinuses. Third radials, in two of the 

 arms seen, small, and bearing on each of their superior sloping sides, a long, 

 very slender, subcarinated arm, which bifurcates on the second piece abo 

 while the divergent divisions subdivide two or three times again above, at in- 

 tervals of three or four pieces ; the divisions and subdivisions all being 

 slender, and composed of joints about twice as long as wide. In two of the 

 rays seen, however, the free arms are simple from their origin on the first 

 radials, at least as far up as to the sixth piece, inclusive, (which is as far as 

 they can be traced in the specimen), and present the remarkable character of 

 having the second, third and fourth pieces greatly dilated, or alate on each 

 side, so as to be nearly two-thirds as broad as the whole body below ; though 

 the first piece next the body (second radial), is narrow, and nearly twice as 

 long as wide, as are the fifth and sixth pieces. Surface smooth, or only finely 

 granular; sutures close fitting, or not channeled. Anal plate and column 

 unknown. 



Height of body, 0-20 inch ; breadth of do., 0-34 inch ; breadth of the dilated 

 part of one of the simple arms, about 0-22 inch. 



It is possible that the dilated arms may bifurcate above the sixth piece, 

 though the specimen from which the description is made out is not in a con- 

 dition to enable us to settle this point. The fact that they become suddenly 

 narrow above the fourth piece, would seem to indicate that tbey may possibly 

 assume the character of the other arms farther up. As seen lying partly 

 imbedded in the matrix, with the long-jointed, slender arms and their branches 

 incurved, above the little globular body, the whole reminds one very much of 

 the Jurassic genus Saccosoma, Agassiz. 



The very remarkable characters of the arms in this little crinoid, if not due 

 to abnormal development, would certainly seem to warrant its separation, at 

 least subgenerically, from the typical forms of Cyathocrinites. It also seems 

 very improbable that its ventral disc is constructed as in the typical forms of 

 that genus. Should other specimens show the peculiarities we have men- 

 tioned to be normal, we would propose for this type the generic or subgen- 

 eric name Saceosomopsis. 



Specifically this form, at least so far as regards its body, seems to be exactly 

 like a species described by Prof. Hall, under the name Cyathocrimcs parvibra- 

 chiatus (Jour. Bost. Soc. Nat. Hist.., Vol. vii, p. 395, 1861) ; and it is worthy 

 of note, that he describes its " subrachial" or free radial pieces as being 

 "two to each ray, broad and strong, but varying in the different rays." As 

 these pieces " vary in the (liferent rays," may not those he saw, that were broad 

 and strong, have belonged to dilated simple rays, as in our species, and these 

 rays been^broken off above the second pieces, in the specimen described? 1 

 so", his species would almost certainly belong to the same group as ours, but 

 differs specifically in having its bifurcating arms shorter, more rapidly dimin- 

 ishing in size, with shorter pieces between the bifurcations, so as to bring the 

 subdivisions closer together ; also in having larger and deeper sinuses in its 

 first radials for the reception of the second. 



We are much inclined to believe there is a little group of species having 

 essentially the form of body, and the peculiarities of the arms we have de- 

 scribed, and that it will probably include Cyathocrinites Saffordi, the arms ot 

 which are unknown. 



1870.] 



