26 PROCEEDINGS OF THE ACADEMY OF 



Locality and position. Crawfordsville, Indiana. Keokuk division of the 

 Lower Carboniferous series. The specimen from which our description was 

 made out belongs to the collection of Mr. Corey. 



Poteriocrinites (Zeacrinus?) concinnus, M. and W. 



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, rouud, and composed near the 

 base of thin pieces. Subradials of moderate size, not thickened or tumid, 

 four hexagonal, and one on the anal side heptagonal. First radials as wide 

 as the subradials, but shorter, pentagonal, and truncated their entire breadth 

 above. Second radials as wide as the first, but scarcely more than half as 

 long, all transversely oblong in form. Third radials in the posterior and 

 anterior lateral rays, of nearly the same size and form as the first, but of 

 course with the sloping sides above. On these sloping sides they each sup- 

 port two unequal arms, the posterior one of which in one of the posterior 

 lateral rays is smaller than the other, and can be seen to bifurcate on the 

 fourth piece, while the other bifurcates on the second piece, and its subdi- 

 visions divide again at various distances above, several times, so as to make 

 altogether about thirteen or more subdivisions in this ray. The anterior main 

 division of one of the anterior lateral rays can also be seen to bifurcate on 

 the fifth piece above the tbird radial, and one of its branches subdivides at 

 different distances above into three subdivisions, and the other into four. 

 Anterior ray simple to the eighth piece, the pieces between the first and last 

 being short and somewhat wedge-form, while the last is pentagonal and sup- 

 ports two arms, each of which can be seen to bifurcate at least once some 

 distance above. Anal pieces with the usual double alternating arrangement, 

 the lowest piece being obliquely inserted between the upper sloping sides of 

 two of the subradials, and partly under one side of one of the first radials, 

 while a contiguous piece on the left above is supported on an upper truncated 

 side of one of the subradials, and the latter are succeeded by others that con- 

 nect with the base of the proboscis. 



Arms long, slender, very straight, and gradually tapering; slightly convex 

 on the dorsal surface, and flattened so as to fit closely together on each side, 

 with all their divisions running up parallel, or showing scarcely any divergence 

 at the bifurcations, and all composed of short wedge-formed pieces ; axillary 

 pieces not more protuberant than the others. Pinuulae small, and arising one 

 from the upper part of the longer side of each arm piece, alternately on each 

 side, and rather closely approximated to each other. 



Surface, in well preserved specimens, finely and obscurely granular, the 

 granules showing on the arms (as seen under a magnifier) a tendency to 

 arrange themselves in longitudinal rows, or to assume vermicular forms. 

 Sutures between all the pieces merely linear. 



Entire length of arms and body, 2-80 inches; height of body to the top of 

 first radials, 0-27 inch; breadth about 0-43 inch. Thickness of column, at its 

 connection with the base, 0-17 inch. 



This species seems to combine, to some extent, the characters of Poteriocri- 

 nites and Zeacrinus. In general habit, especially in the somewhat flattened 

 and closely contiguous characters of all the divisions of its arms, all around, 

 when folded together, as well as, to some extent, in their mode of division, it 

 reminds one of many species of Zeacrinus. In the form of its body, however, 

 and particularly in having three primary radials, instead of only two, in each 

 of the anterior lateral and posterior lateral rays, and about eight below the 

 first bifurcation in the anterior ray, as well as in the general form of its body, 

 it agrees more nearly with the typical forms of Poteriocriniles. We know of 



[April, 



