156 FOSSIL CRINOIDS. 



of extraordinary size, belonging to some Crinoid as yet undescribed; and it is 

 the specimen figured herein on Plate V, fig. 2. Looking further through the 

 collections, we found the specimens figured at \n, b of the same plate, which 

 showed clearly where the first one belonged. Dr. Schuchert courteously re- 

 quested me to describe the species, and placed the specimens in my hands for 

 that purpose. My apologies are due him for having delayed its publication 

 until now, owing to press of other work. I have since unearthed, among material 

 quarried for me at Crawfordsville by Frederick Braun, some other specimens 

 which supplement those of the Yale Museum in various particulars. 



The size of this remarkable Crinoid is shown in the figures, which are all of 

 natural size; and the ventral sac is developed to a degree of extravagance no- 

 where else observed. It is a mere enlargement of the structure of P. doris, 

 but the ribs due to the median ridge of the plates, instead of being merely indi- 

 cated by elevation of the folds, have come out from them, and look like arms. 

 But even more striking than the size — which is not confined to one specimen, 

 but seems to be the rule in six specimens out of eight — is the extraordinary 

 fragility of the calcareous structures in so large a Crinoid; there seems to be no 

 surface of apposition between the calyx plates, which thin out to a knife edge 

 at the sutures; the union must have been by long hgamentous bundles attached 

 in folds or fossae back from the edge. This necessarily made an extremely 

 weak and pliant wall, and as a result the specimens, although imbedded in a 

 very soft matrix, are invariably flattened to a thin mass. Allowing for this 

 flattening, the sac in Fig. 2, PI. V, must have been nearly two inches in diameter. 

 The plates composing the sac are of extreme shortness, being about 1 mm. in 

 length in the median portion of the sac. 



I was at first under the impression that the specimens figured as 1 and 2, of 

 Plate V, probably belonged to the same individual; but the presence of the 

 commensally attached Platyceras shows that they are not, for the beak of the 

 shell is perfect in Fig. 1, and that part is left intact in Fig. 2, being visible at 

 the lowest corner. Taking the portions of the shell in the two specimens for a 

 guide, I think they are placed in about the same relative positions on the plate 

 that they should have had if belonging together; from the great width between 

 the ribs at the upper edge, it is evident that the sac extended much higher up, 

 and judging by the taper of the upper end, as shown by Fig. 3, it may have been 

 as much longer as the part preserved, thus making the whole crown at least 12 

 inches high. The Platyceras is found attached in nearly all the specimens at 

 about the same height; as its location was for the purpose of feeding upon the 



