DESCRIPTIONS OF THE SPECIES. 289 



up the columnar cavity at the base. Neither do we agree with them as to the 

 disposition of the hydrospire-clofts in relation to the ambulacra, a point to which we 

 have already alluded on pp. 98, 99 1 . We can give a general confirmation to Dr. White's 

 description of the summit plates 2 ; and we agree both with him and with Messrs. 

 Meek and Worthen 3 that these pieces did not possess the mobility necessary to 

 their being opened and closed at will. On the other hand, we have not been fortunate 

 enough to observe anal covering plates, except perhaps in one of Mr. Wachsmuth's 

 specimens ; nor have we seen any definite traces of an anal tube or proboscis in 

 Orophocrinus, and presumably in this species, as described by Messrs. Wachsmuth 

 and Springer 4 . If the anal plates are arranged in the form of a small tube or 

 proboscis, we can quite reconcile their statement with Dr. White's description by 

 supposing that in his specimens the plates were accidentally pressed within the 

 opening. 



A remarkable feature in 0. stelliformis is the distance between the proximal side 

 plates and the radial centre (PI. XV. fig. 11). It is more apparent in this than in 

 any other species of Orophocrinus, but there area series of gradations between it and 

 0. pentangularis, in which the intervening space is least (PL XV. fig. 8). 



We have indicated the points which distinguish this species from Orophocrinus 

 vents, Cumb., sp., in the description of the latter type. 0. gracilis, M. & W. 5 , is 

 at once separated by the more strictly Pentremite-like outline of its calyx. 



Localities and Horizon. Burlington, Iowa ; Lower Burlington Limestone, Subcar- 

 boniferous. [Shumard 6 also gives Hannibal, Missouri ; and Monmouth, Illinois.] 



Orophocrixus stelliformis. var. campaxulatus, Eambach, var. 

 (PL XVI. fig. 5.) 



Codonites campanulatus , Harnbacli, Trans. St. Louis Acad. Sci. 1884, vol. iv. no. 4, p. 553, 

 t. D. f. 8, 9. 



Remarks. Two small specimens in the Collection differ from the typical 0. stelli- 

 formis in possessing a bell-shaped body, shorter ambulacra, longer and less concave 

 sides between the basiradial suture and the radial lips, which are less prominent than 

 in the type (PL XVI. fig. 7). These individuals appear to us to correspond with 

 Mr. Hambach's Codonites campanulatus, which we take to be only a variety of 

 0. stelliformis, and not a distinct species. We do not think that there is a much 



1 Ann. & Mag. Nat. Hist. 1883, vol. xi. p. 236. 



2 Boston Journ. Nat. Hist. vol. vii. no. 4, p. 486. 



3 Proc. Acad. Nat. Sci. Philad. 1869, p. 85. 



4 Revision of the Palseocrinoidea, Part II. 18S1, p. 18, note. 



5 Report Geol. Survey Illinois, vol. v. t. 8. f. 6. 



6 Trans. St. Louis Acad. Sci. 1858, vol. i. no. 2, p. 247. 



2p 



