HODSON-RIVER GEOUPi 277 



Genus D I S C P II Y L L U M. 



[Greek, (Sio'xos, a disc, and (jjuXXov, a leaf.] 



Character. Discoidal, flattened, rays or disscpiniciits numerous, proceeding from the 

 centre; body of the fossil apparently semicalcareous or corticiferous ; margin well defined. 

 From the semi-metamorphic condition of the rock, it is impossible to determine whether 

 this body was calcareous ; but it appears to have been otherwise. 



335. 1. DISCOPHYLLUM PELTATUM (n. s;;.)- 

 Pl. LXXV. Fig. 3. 



Body consisting of a somewhat circular flattened expansion, composed mainly of radiating 

 fibres, which enlarge as they recede from the centre, and terminate in a thickened border. 



This fossil appears to have consisted, originally, of a semi-hard circular or oval body, 

 with firmer rays, reaching nearly or quite to the margin. The body becomes thicker and 

 apparently harder towards the margin, and the rays are nearly concealed in its substance. 

 This disc may have been attached by a smaller stipe, proceeding from the lower side, 

 some obscure evidence of such an appendage existing. 



Two specimens of this peculiar fossil have been found : one in 1822, and the other a 

 few years since, showing that it is an exceedingly rare form. It is (juite unlike any other 

 fossil known in our older strata. 



Position and locality. This species occurs in the partially metamorphic arenaceous shales 

 of the Hudson-river group, near the Nail Factory, below Troy, where the only known 



specimens have been found. , (Cabinet of Tray Lyceum; Cabinet of Prof. Cook.) 



336. 1. (Undetermined.) 



Pl. LXXV. Fig. 1. 



The specimen figured is an impression of the outer surface of some incrusting coral, 

 frequently foiuid attached to the shell of tlie Orthoceras coralliferum. It appears to be 

 composed of large elevated points or stars, with an intermediate granulated or papillose 

 surface. It is usually obscure, or very imperfectly preserved, the more elevated points only 

 being visible. The figure is of the natural size, from a specimen adhering to an Orthoceras. 

 This coral is also represented in an imperfect specimen attached to another shell of tlie 

 same species (Plate Ixxxvi, fig. 1 ) . It is sometimes found under other circumstances, and 

 attached to other shells, but always so obscurely preserved that its characters cannot be 

 well determined. 



Position and locality. Tiiis coral is known in many localities of the Hudson-river group, 

 widely separated from each other. It has been found at Turin, Pulaski, Loraine ; near 

 Rome, in Oneida county ; in the altered shales near Waterford, and in the same situation 

 in Ohio, near Cincinnati, C^'"'' Collection.) 



