NOTES ON AN UNUSUALLY FINE SLAB OF FOSSIL 

 CRINOIDS. 



By R. S. Bassler. 



Curator, Division of Paleontology, United States National Museum. 



A large slab of fossil crinoids just prepared for the exhibition collec- 

 tions in the Division of Paleontology of the United States National 

 Museum is so unique and of such mterest that it seemed to the writer 

 worthy of some special notice. This slab belongs to the unrivaled 

 collection of fossil echinoderms deposited m the National collections 

 by Mr. Frank Springer, who is preparing a monograph upon Scypho- 

 crinus, the genus to which the crinoids represented on the slab 

 belong. Mr. Springer has very kindly allowed the writer free use of 

 his notes upon this genus in preparation of the present article. 



For over 50 years paleontologists have known of certain bulblike 

 crinoidal or cystoidal bodies in late Silurian and early Devonian 

 rocks. American specimens were described by Hall in 1879 as 

 Camarocrinus, but some years before Barrande applied the name 

 Loholithus to similar objects in the Silurian rocks of Bohemia. A 

 large number of these bodies having been accumulated in the col- 

 lections of the United States National Museum, Prof. Charles Schu- 

 chert in 1904 published a full account of them in his paper on 

 "Siluric and Devonic Cj^stoidea and Camarocrinus." ^ HaU regarded 

 Camarocrinus as a large chambered bulb to which was attached a 

 column bearing at its distal extremity a large crinoidal calyx with 

 unknown characters. Schuchert arrived at substantially the same 

 conclusion, believing that '^Camarocrinus thus appears to be the float 

 of an unknown crinoid that was held together after the death of the 

 individual by the firmly interlocked double walls of the exterior and 

 interior while the crown and stalk dropped away. Under this 

 hypothesis the float drifted with the sea currents, was finally fiUed 

 with water, and the attenuated end being heavier sank in that posi- 

 tion to the sea bottom." Although realizmg that the last word had 

 not been said m regard to Camarocrinus, this author believed that the 

 supposition that these bodies were anchored in the mud with the 

 stalk directed upward was not in accord with the facts. In Bohemia 



> Smiths. Misc. Coll., vol. 47, 1904, pt. 2, pp. 201-272, 11 pis., 24 figs. No, 1482. 



Proceedings U. S. National Museum, Vol. 46— No. 2009. 



57 



