NATURAL SCIENCES OP PHILADELPHIA. 159 



it Cyathocrinus Norwoodi, since the absence of the large trunk-like summit, 

 and the presence of a slender lateral proboscis, are characters probably of more 

 importance, than the presence of a few more anal pieces and the differences in 

 the form of the body. 



Named in honor of Prof. J. G. Norwood, of the University of Missouri. 



LocaUty and position. Hancock Co., Illinois. St. Louis division of the Sub- 

 carboniferous series. 



POTERIOCRINDS (ScAPHIOCRINDS) SUBTUMIDUS, M. & W. 



Body basin-shaped below the summit of the first radial pieces, three times as 

 wide as high, composed of thick tumid plates. Basal plates very small, deeply 

 impressed, and hidden by the column. Subradials comparatively large, very 

 convex, and extending out nearly horizontally, but curving upward at their 

 outer extremities; about as long as wide, three of them subhexagonal, and two 

 subheptagonal, the angle at the basal or inner side being nearly obsolete. First 

 radials convex, about twice as large as the subradials, half as high as wide, 

 regularly pentagonal, and all nearly evenly truncated above, their emire breadth. 

 Anal plates like the others, tumid; first one one half to one-third as large as 

 the subradials, irregularly pentagonal, and resting obliquely beneath one side 

 of a first radial, between the upper sloping sides of two subradials, while its 

 left and upper side connect with the other anals. Second anal piece .resting 

 upon the truncated upper side ot one of the subradials, and connecting on the 

 left with a first radial, above which it projects nearly half its length. Third 

 anal piece hexagonal, supported upon a shoit truncated upper side of the first 

 anal, and connecting on the left with the second, and on the right with a first 

 radial, above which it projects a little. 



Second radials and parts above unknown. Surface smooth ; sutures strongly 

 defined, in consequence of the tumid character of the body plates. 



Height of body to summit of first radial pieces, 0-27 iuch ; breadth of do. 

 O-TS inch; breadth of base, 0-13 inch. 



Until specimens of this species can be examined, showing the struc'ure of the 

 parts yet unknown, it will be difficult to determine whether its name should 

 not be more properly Zeacrinus subtumidus, or whether it may not belong to 

 another group, of which Graphiocrinus li-brachialis, of Lyon, is the type* 



This latter form differs widely, not only from Poteriocrinus proper, but from 

 Scaphiocrinus, Zeacrinus, and also from Graphiocrinus, in having its arms com- 

 posed each of a double series of interlocking pieces, as well as in its unusually 

 massive tumid plates and general physiognomy. In some families of the Cri- 

 noidea, such for instance as the Platycrinus group, a difference like this in the 

 structure of the arms may be of less importance, but in that including Poterio- 

 crinus and the allied genera, we believe it to be of more significance, if not 

 indeed of generic value, especially when accompanied by the other differences 

 of habit presented in this instance. Hence we would propose fur this group 

 the name Eupachycrinus, with Eupachycrinus 14- brachialis = {Graphiocrinus 14- 

 brachialis, Lyon) as the type. It will also doubtless include E. pentalobus = 

 (Cyathocrinus? pentalobus, Hall,) and possibly also Scaphiocrinus orbicularis, Hall. 



Should our species here under consideration prove to have its arms con- 

 structed of a double series of pieces, we should unhesitatingly call it Eupachy- 

 crinus subtumidus, since in the massive tumid character of its body pieces, small 

 sunken base, and general form and appearance, it agrees, so far as its parts are 

 known, essentially with the type of that group. Specifically, however, it will 

 be readily distinguished by its subradial pieces being proportionally smaller 

 and so much less protuberant as to give a different outline to the under side 

 of the body, as seen in a side view. It also differs entirely in the form and 

 arrangement of its anal pieces. 



Locality and position. Bay City, Pope Co., Illinois. Chester division of the 

 Subcarboniferous series. 



* See Kentucky Geological Eeport, vol. iii. p. 477, pi. i. figs. 2 and 2a. 



1865.] 



