at 



rest all 



>ue 



y well 

 be the case so far as lie is concerned; for he had originally 



15. 



* Joum Acad. Nat. Sci. Philad. vol. viii. p. 280, pi. xv. %. 17. ' 

 t Fifteenth Annual Report N. York State Cab. 1862. t. i. Hg>. 14 and 





228 Messrs. E. Etheridge, Jim., and P. H. Carpenter on 



figures. In reality, however, the whole surface between the 

 food-groove and the cleft is formed by side plates. But the 

 divisions between them are much more marked near the food- 

 groove than they are near the cleft. In fact the broad outer 

 portions of the plates seem to coalesce so completely that they 

 look like portions of the calyx-plates intercalated between the 

 sides of narrow ambulacra and the clefts, as implied in the 

 quotations given above. 



But in one specimen we have found that the side plates are 

 readily separable ; and then it is apparent that their outer 

 portions really belong to the ambulacra, and are not parts of 

 the calyx-plates. An approach to this condition occurs in the 

 Belgian 0. Orbignya7uis y in which there is a sort of thick- 

 ened rim to the wide ambulacrum ; but it appears to be 

 chiefly formed by the outer side plates, of which, like Meek 

 and Worthen, we have not succeeded in finding any definite 

 trace in 0. stelUfonnis. 



Somewhat before the middle of the ambulacra the side- 

 plates begin to diminish very rapidly in size, and the hydro- 

 spire-clefts consequently approach more closely to the linear I 

 median portions of the ambulacra. Their length seems to 

 vary considerably in different individuals ; but some little 

 way before the end of the ambulacra the side plates meet the 

 radials and obliterate the clefts altogether. 



3. Remarks upon the Genus Eleacrinus [Bomer^ 1S51)* 



Kucleocrinus, Conrad, 1842. 

 Olivanites, Troost MS., 1849. 



It appears to us, for reasons which are stated below, that 

 Burner's name is the one by which this type ought to be 

 known. Conrad's description * of it under the name of Nu- 

 cleocrimis runs as follows : — u This genus differs from Pen- 

 trendies. Say, in having only one perforation at top which is 

 central." He gave a figure of his one species, N. elegans, 

 though no description accompanied it; and a comparison of 

 this figure with one published later by Hall f shows that the 

 fossil is represented in an inverted position. We infer from 

 this that the " central perforation at top " is really what Hall 

 described as " the concavity at the point of attachment of the 

 column." He says nevertheless that Conrad's figure " sets 



tion as to the fossil intended." This may very w 









