4(50 REMARKS ON NEW SPECIES OF CRINOIDKA, 



radials are very small ; four times as broad as high. The third radial s are larger than the 

 second ; flat ; cuneiform ; very low, or short on their vertical margin ; each of these sup- 

 port the first piece, or the base of the free rays. The free rays rise singly, one on each 

 radial series ; they are composed of rather large, thin, semicircular pieces, which abut 

 squarely against each other at the centre of the back of the rays ; the pieces of the ray do 

 not interlock with each other, so far as they are preserved on the examples observed. No 

 part of the dome is attached to any specimen seen ; its form and arrangement is unknown. 

 All the plates of the body are very thin, except near the attachment to the column and 

 the arms. 



Column round, composed of circular pieces ; the smaller ones are about three times as 

 thick as the larger pieces. The pieces are alternately disposed, thicker and thin ones. 

 The thin pieces are enormously expanded ; some have been observed surrounding a small 

 one — two-twentieths of an inch in diameter — that were nearly an inch in diameter, of 

 a thickness not greatly exceeding one hundred to the inch, the enlarged pieces still retain- 

 ing their perfectly circular outline. These rounded, disk pieces, surrounding a small 

 columnar piece, was for many years a mystery ; their connection could not be traced to 

 any known crinoidal body until the discovery of the specimen figured, Plate II, Fig. g 1, 

 showed their connection with Platycrinus Leai, of this paper. 



Size of Specimen. 



INCH ES. 



Height of basal cup, 27 



Height to summit of first radials, 70 



Diameter at summit of first radials, ....... .1)7 



Diameter of columnar facet, ........ .20 



Height of second and third radial pieces, ...... .12 



Width of third radial pieces, ........ .22 



Locality and Geological Position.— 7"Uppcr crinoideal limestone, Bear Grass Quarries, Jefferson County, 

 Kentucky. Fragments abundant; good specimens very rare. The epidermis, or muscular covering, 

 which no doubt in life covered all crinoideans, and upon which the ornamentation found on so great 

 a number of these bodies, in such exquisite beauty and variety, is placed, does not appear to have 

 been preserved on any fragment of the specimens recovered. Under a strong lens, obscure stria; aro 

 observed on some parts of some of the larger plates. 



The rocks of this locality, which are of great thickness in New York, in the geological 

 horizon immediately above the Niagara group, are here quite thin ; and there is a min- 

 gling in these beds of the fossils of the Niagara, Upper and Lower Hildcrburgh, &c., to 

 the base of the black slate.* The entire thickness of these beds, at localities where the 



* Genesee slate. See Vol. II, Illinois Ecports, Introduction, p. 8. 



