490 PALEONTOLOGY OF ILLINOIS. 



smooth, or only finely granular. Sutures close fitting, or 

 not channeled. Anal plate and column unknown. 



Hight of the 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. (See note below.) 



Position and locality Keokuk group ; Crawfordsville, Indiana. 



GENUS POTEKIOOKIKITES. 



POTERIOCRINITEB (ZEACRLNUS'?) CONCINNTJS, M. and W. 



PI. 14, Fig. 3. 



Poteriocrinites (Zeacrinusl) coneinnun, MEEK and WORTHEN, 1870. Proceed. Acad. Nat. Sci., 

 Phila., p. 26. 



BODY wider than high, rather rapidly expanding upward 

 from the column. Base small, basin-shaped, about three 

 times as wide as high, and truncated about three-fourths 

 its breadth below by the facet for the attachment of the 

 column. Basal pieces wider than high, pentagonal in form, 

 and expanding upward from the column, which is rather 

 stout, round, and composed near the base of thin pieces. 

 Subradials of moderate size, not thickened or tumid, four 



NOTE. It is possible that the dilated arms may bifurcate above the sixth piece, though the speci- 

 men from which the description was made out is not in a condition to settle this point. The fact that 

 they become suddenly narrow above the fourth piece, would seem to indicate that they may possibly 

 assume the character of the other arms further 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 Saecosoma, Agassiz. 



The very remarkable characters of the arms in this little criuoid, if not due to abnormal develop- 

 ment, would certainly seem to warrant its separation, at least sub-generically, from the typical forms 

 of Cyathocrinites. It also seems very improbable that its ventral disc is constructed as in the typical 

 forms of this genus. Should other specimens show the peculiarities we have mentioned to be normal, 

 we would propose for this type the generic or sub-generic name Saccosomopsis. 



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 Gyathocrinus parvibrachiatus (Jour. Boat. Soc. Nat. Hist., Vol. VII, 

 p. 395, 1861,) and it is worthy of note that he describes its " subbrachial " or free radial pieces as 

 being "two to each ray, broad and strong, but varying in the different rays." As these pieces ' earn 

 in tlie different rays," may not those he saw, that were broad and strong, have belonged to dilated, .sim- 

 ple rays, as in our species, and these rays been broken off above the second pieces in the specimen 

 described ? If so, his species would almost certainly belong to the same group as ours, but differs 

 specifically in having its bifurcating arms shorter, more radidly diminishing 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 described, and that it will probably include Oyathocrinus 

 Xa/ardi, the arms of which are unknown. 



