NOTES ON AN UNUSUALLY FINE SLAB OF FOSSILCRINOIDS.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 NationalMuseum is so unique and of such mterest that it seemed to the writerworthy of some special notice. This slab belongs to the unrivaledcollection of fossil echinoderms deposited m the National collectionsby Mr. Frank Springer, who is preparing a monograph upon Scypho-crinus, the genus to which the crinoids represented on the slabbelong. Mr. Springer has very kindly allowed the writer free use ofhis notes upon this genus in preparation of the present article.For over 50 years paleontologists have known of certain bulblikecrinoidal or cystoidal bodies in late Silurian and early Devonianrocks. American specimens were described by Hall in 1879 asCamarocrinus, but some years before Barrande applied the nameLoholithus to similar objects in the Silurian rocks of Bohemia. Alarge 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 regardedCamarocrinus as a large chambered bulb to which was attached acolumn bearing at its distal extremity a large crinoidal calyx withunknown characters. Schuchert arrived at substantially the sameconclusion, believing that '^Camarocrinus thus appears to be the floatof an unknown crinoid that was held together after the death of theindividual by the firmly interlocked double walls of the exterior andinterior while the crown and stalk dropped away. Under thishypothesis the float drifted with the sea currents, was finally fiUedwith water, and the attenuated end being heavier sank in that posi-tion to the sea bottom." Although realizmg that the last word hadnot been said m regard to Camarocrinus, this author believed that thesupposition that these bodies were anchored in the mud with thestalk 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
58 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.46.Camarocrinus (Lololithus) is found associated with calices of thecrinoid ScypJiocrinus, and in 1900, Dr. F. A. Bather definitely asso-ciated these two genera as parts of one and the same organism.No association of Camarocrinus and Scypliocrinus in America hadever been noted, although the Camarocrinus occurred frequently in suchlarge numbers as to make up entire limestone layers. In Oklahoma,where these layers sometimes outcrop at the surface, cobblestone-Hke masses frequently strew the ground in great profusion. Since1904 Mr. Springer has directed his efforts toward the discovery ofnew evidence upon Camarocrinus, with the result, as announced atthe 1912 meetmg of the Paleontological Society in New Haven,Connecticut, that he is now able to show, fu"st, that the genus Scy-
'pJiocrinus occurs at several horizons in the late Silurian and earlyDevonian of America; second, that the Camarocrinus bulbs are fre-quently connected at the distal end of the stem with crinoidsbelongmg to the genus ScypJiocrinus; and thu'd, that these bulbsusually occur with the stalk end upward and not downward asbefore supposed. Mr. Springer will publish the evidence for theseconclusions later, but a few notes regarding the slab which is thesubject of the present' article are in order.Durmg the summer of 1904, as recorded in Schuchert's paper, thepresent writer observed Camarocrinus m the bluffs along the Missis-sippi Kiver a few miles north of Cape Girardeau, Missouri, in theoutcropping edge of a layer with numerous large crinoid stems. In1911 Dr. E. O. Ulrich found a detached mass of crinoidal limestonefrom the same layer in which was embedded the well-preserved calyxof a large ScypJiocrinus. These discoveries were so promising offavorable results that Mr. Sprmger asked his private collector,Mr. Frederick Braun, to carefully examine this general area m thehope of findmg the fossiliferous bed at some place sufficiently exposedfor careful collectmg. After a protracted search along the bluffsfacing the Mississippi River, Mr. Braun finally succeeded in locatingthe crmoidal layer at a point where he could carry on quarryingoperations. Here several weeks' work resulted not only m somemost remarkable specimens of crinoid, but in settlmg finally thefacts upon which the mterpretation of Camarocrinus must depend.The work was of no small difficulty, as the physical obstacles wereformidable. The layer could be readily traced but it was not every-where fossiliferous, and as the crinoids occurred only on the lower sidea place had to be found where there was a soft seam underneath alongwhich the fossiliferous stratum would readily separate from the onenext below. The fossiliferous part of the layer proved to be limitedto a smaU area which contained the remains of a thickly crowdedcrinoid colony suddenly killed by some change in the water andembedded in the soft muddy sea bottom mthout material disturbanceby currents.
NO. 2009. A FINE SLAB OF FOSSIL CRIN0IDS?BA8SLER. 59Four large slabs ranging from 500 to 1,500 pounds weight eachand a number of smaller pieces were selected, the whole weighing4,500 pounds. Two of the slabs fit together, forming a single one ofabout 4 by 7 feet, containing the most important specimens. Thisis the slab now on exhibition in the United States National Museum.The remaining specimens have been prepared and form a part of thestudy series.The locality was a number of miles distant from any station orlandmg, and it was necessary to transport lumber to make strongpacking cases for the slabs, embedding them m plaster to insure thespecunens from injury m handling. A chute was then constructedto slide the cases down with ropes and tackle from a rock levee tothe water's edge, about 35 feet distant, where they were shipped ona passmg river steamboat. Upon their arrival at the NationalMuseum it was necessary to clear away the adherent clay with finetools before the specimens could be seen or studied. In addition alarge amount of time was consumed in removing the more or lesshard calcareous matrix composed of innumerable arm and pinnulejoints forced down between the arms of the specimens and firmlycemented by pressure.The principal slab, of which a portion, one-sixth natural size, isshown on plate 1, contains 18 complete crowns, several of them withthe stem attached for part of its length. Some have the calyx fairlyrotund, but most of them are considerably flattened and often muchdistorted by contact with the Caniarocrinus bulbs noted below. AUhave the strong, many-branched arms intact and often upward of12 inches long. Two of the smaller but more complete calices, one-half natural size, are shown on plate 2. Besides these crowns sev-eral sets of arms are partly visible, belonging to calices which areentirely buried, either under other individuals or m the limestonematrix, which becomes fu-m and hard a short distance inward. Someparts of the slab are covered with a dense mass of stems lying parallellike stalks of grain in a sheaf, and many of the crowns lie with theirarms pomting in the same direction, as if they had fallen over in themud at the same time under the common impulse of a gentle current.Intermmgled with the crowns and stems forming the chief remainingportion of the crowded surface are numerous Camarocrinus bulbs;some of them are well exposed and appear of good size, while inmany cases only a part can be seen protruding among the otherobjects. All of them are considerably flattened and some much frac-tured from the pressure of the overlying mass of arms of the compactlimestone deposit forming the main thickness of the heavy layer.This slab has been mounted on a flat-topped glass-covered baseand has been mstalled at the west end of the hall of InvertebratePaleontology. Here the specimen serves a twofold purpose?^first,in showing one method of fossilization, and, second, as an introduc-tion to the biologic exhibit of fossil crinoids.

PROCEEDINGS, VOL. 46 PL 1
V" V
Mm- P^"
Slab of Scyphocrinus. (One-Sixth Natural Size.For explanation of plate see page 59.

U. S. NATIONAL MUSEUM PROCEEDINGS. VOL. 46 PL. 2
Two Complete Calices of Scyphocrinus. (One-Half Natural Size.For ExPb?,NATioN of plate see page 59.