NATURAJO SCIENCES OF PHILADELPHIA. 139 



ceeding radials. Anal pieces presenting the usual arrangement of a double 

 alternating series, the lowest being partly under one side of the first radial on 

 the right, while the next on the left of this rests on the truncated upper edge 

 of one of the subradials, and these connect with others above, that form the 

 base of the proboscidiform ventral extension. Second radials very small and 

 short, or scarcely more than filling the sinuses in the first. Third radials 

 nearly as wide as long, quadrangular and only about half as wide as the first 

 radials. Fourth radials a little larger than tlae third, pentagonal in form, and 

 supporting the arms on their superior sloping sides. 



Arms slender, rounded and proportionally long, bifurcating first above the 

 last radial, generally on the third or fourth piece, above which each of the 

 subdivisions bifurcates again several times. Arm pieces generally about as 

 wide as long, and not wedge shaped. 



Proboscidiform extension at least half (and perhaps more than half) as long 

 as the arms, entirely lateral, and not more than half as wide as the body, 

 below ; apparently somewhat thicker above. Body plates not convex, but 

 merely granular, and joined by close fitting sutures. Column slender, round, 

 and composed of nearly equal moderately thicli pieces, near the base. 



Height to top of first radial pieces, about 0-15 inch; breadth, 0-24 inch ; 

 length of arms, about 0-95 inch. 



This is one of those few intermediate types such as we occasionally meet 

 with in various departments of Natural History, when extensive collections 

 can be studied, connecting or standing, as it were, intermediate between two 

 genera. That is to say, it combines some of the characters usually regarded 

 as belonging especially to Poteriocrini'es with others equally characteristic of 

 Cyathocrinites. Its body has much the usual form of Cyathocrinites, with the 

 double alternating series of anal pieces precisely as we see in Poteriocrinites. 

 On the other hand, it has the narrow, decidedly lateral proboscidiform ventral 

 extension of Cyathocrinites, and might, with almost equal propriety, as far as 

 we yet know, be called Cyathocrinites ? perplexus. The existence of such a type 

 would, in the estimation of some naturalists, be regarded as a sufficient reason 

 for uniting the genera Poteriocrinites and Cyathocrinites. In this opinion, how- 

 ever, we cannot concur, for we believe that if all the genera thus connected by 

 a few obscure forms were united, it would be found impossible to fix any limits 

 whatever to such groups, with all the extinct types before us. Possibly char- 

 acters may be found, however, warranting the establishment of a new genus 

 for such forms. 



Specifically this little Crinoid seems to be most nearly allied to our Cyatho- 

 crinus ? enormis, but it differs in the number and arrangement of its anal pieces, 

 as well as in having its arm pieces scarcely one-half as long in proportion to 

 thickness. 



Locality and position. — Lower part Burlington group of the Lower Carbon- 

 iferous, Burlington, Iowa. No. 264 of Mr. Wachsmuth's collection. 



Subgenus SCAPHIOCRINUS, or GRAPHIOCRINUS. 

 ScAPHiocRiNus RUDis, M. and W.* 



Body much depressed, about four times as wide as high, flat or a little con- 

 cave below, the flattened part including the basal, subradial, and about half 

 the length of the first radial pieces. Base very small, a little impressed, and 

 entirely hidden by the column. Subradial pieces of moderate size, extendieg 

 out horizontally from the column ; the one on the anal side, however, curving 

 up distinctly, and the others slightly, at the ends ; all flat, excepting the cur- 

 vature mentioned, and pentagonal in outline (the superior angle being rather 

 salient), excepting the one on the anal side, which is hexagonal, being trun- 



* Although we write the names Scaphincrinus and Zeacrinus in tills paper for the sake 

 of brevity, as if they were regarded as distinct genera, we really use them as subgeneric 

 names under Poteriocrinites, as already explained. 



1869.] 



