FOSSILS OF THE BfRUXGTOX GROUP. 



I'I.ATYI KIMTES iNru.MiTrs. White. 



Platycrinut ivcomptu*, WHITE, 1863. Jour. Bosi. Soe. Xat. Hist., Vol. VII, p. 503. 



BODY attaining a moderately large size, composed of 

 thick, smooth plates: eiip-shaped, with gradually expanding 

 sides. Base depressed or basin-shaped, with under side 

 somewhat impressed in the region of the facet for the at- 

 tachment of the column ; margins curved up to connect 

 with the body plates above. First radial plates wider than 

 high, wider above than below, with superior lateral angles 

 so largely truncated, to form notches for the interradial and 

 anal pieces, as to present almost an irregular hexagonal 

 form, separated from each other and from the base by more 

 or less channeled sutures: sinuses for the reception of the 

 second radials about half as wide as the upper part of the 

 tirst. and generally not very deeply excavated. Second 

 radials generally rilling, and sometimes more than rilling 

 the sinus in which they rest, and always more than twice 

 a< witlt as high: all curving outward nearly at right angles 

 to the vertical axis of the body. Rays, after dividing on 

 ilie second radials. directed at first nearly horizontally out- 

 ward, each division consisting of two pieces in direct suc- 

 cession, the second one being axillary, and supporting an 

 arm on its outer sloping side, while on its inner sloping 

 side it bears in direct succession two pieces, the second of 

 which is axillary, and gives origin to two arms or divisions, 

 one of which bifurcates a^ain on the second piece, thus 

 making, as far as the specimen shows, seven or eight arms 

 to each ray. Interradial and anal pieces comparatively 

 large. Surface smooth or only tinely granular. 



We have not seen a specimen of this species with the 

 vault exposed, but Dr. WHITE describes it as being rather 

 high, and composed of tumid pieces, the largest of which 

 occupy the central region. The opening, he *ay>. is situ 



