254 Wachsmuth and Springer — Revision of the genus 



the structure of this interesting type of fossils, and it enables us 

 to confirm the opinion of Count Pourtales, thereby rendering a 

 revision of the generic formula and description appropriate and 

 necessary. 



A specimen of B. Pourtalesi, W. & S., has been deprived of 

 the column, and the lower part of the cup is somewhat 

 crushed, in such a manner that two of the long plates are sep- 

 arated along their entire length, exhibiting the sutures to the 

 central perforation which leads into the column. The lower 

 extremities of these plates are excavated, forming a concavity 

 for the insertion of the pentagonal column, the marks of its 

 attachment in a pentagonal outline are plainly visible, thus 

 proving beyond the slightest doubt that these long plates rested 

 directly upon the column, and formed with the first radials, the 

 cup which encloses the visceral cavity. From these facts it 

 follows that the long pieces, which were considered to be sub- 

 In- the author of the genus and by Messrs. Meek 

 and Worthen i'n their description of B. Whitei, must now be 

 ted as basal plates. 

 Additional light has been thrown upon the construction of 

 other parts in this genus ; every one of the four known species 

 is furnished with a strong proboscis, inflated toward the top, 

 and resting upon the single large anal plate which is a part of 

 the wall of the cup. The exact structure of the summit of the 

 calyx has not as yet been made out, but the comparatively 

 massive character of the plates which compose the proboscis, 

 as well as the size of that organ, render it altogether probable, 

 that it was supported by a solid dome. 



The arms, as observed in three of the lour known species, are 

 ten in number. They are provided with long, comparatively 

 heav\ pinnules originating <n\ the louget maruins of large, 

 wedge-form j .int.*. which alternate with other joints of quad- 

 rangular outline, thus giving two rows of pinnules, alternately 

 arranged, to each arm. In "both ot our new species these pin- 

 nules are simple; while those of B. typxs are furnished with* 

 secondare pinnules, which are alternately arranged as the pri- 

 mary pinnules The arms of tlii- u.'im- t-.-ar in proportions 

 and general aspect some resemblance to those of For 

 but they are in fact widely different. In Poteriocrinus, the 

 arms divide upon a bifurcating plate or joint, into equal branches, 



which rest upon the upp. r . t thi> joint ; while in Belemno- 



crinus the branches are true pinnules," and not armlets, they 

 spring from the long latteral margin ot tin sy/vtdal joint, not 

 from its upper sider We have in our possession a specimen 

 which in general aspect somewhat resembles Belem»»- 

 I basal plates form here a cylinder appare 

 almost precisely similar to that of B\ typus, and as the upper 



