FOSSILS OF THE HUDSON EIVER GROUP. 73 



situated just below and between the lower ends of the former, with two 

 medium sized circular ones near the center of the valve, and distant from 

 each other. The external features and habits of the shells, however, 

 certainly form strong distinctive characters, and ones of considerable 

 more than specific importance, and upon these features principally we 

 propose to separate them as a distinct genus, under the name of Schiz- 

 ocrania, hoping to be able, at no distant day, to illustrate more fully 

 their internal characters. 



The features as at present known are given in the following diagnosis : 



Genus SCHIZOCRANIA (new gen.). 



Unarticulated, inequivalve, brachiopodous shells, growing parasitic on 

 foreign bodies, to which they are attached by the close adhesion and 

 anchylosis of the external or inferior surface of the lower valve. Lower 

 valve flat or conforming to the surface to which it adheres ; deeply 

 notched on the posterior side of the center, the notch extending from a 

 point more or less distant from the center of the valve to the posterior 

 margin, where the sides of the slit are widely and distantly separated. 

 Upper or free valve more or less convex, and having a beak terminal on 

 the posterior margin. Surface of the upper valve radiatingly striated in 

 the typical species ; the lower valve concentrically wrinkled. Muscular 

 imprints of the free valve, six known ; two of which are situated near 

 the rostral portion of the valve, large, ovate, and diverging ; two minute, 

 approximate, just below and between the former ; and two of medium 

 size, circular, distant from each other, and situated near the center of 

 the valve. Those of the lower valve unknown. Type, S- filosa=Or- 

 bicula f filosa, Hall. The striated surface, widely notched lower valve, 

 and parasitic habits are the strong distinctive points. 



The genus, so far as at present known, is confined to the Silurian for- 

 mations. 



SCHIZOCEANIA FILOSA. 

 PL 1, figs. 12-15. 

 OrUcula f filosa, Hall; Pal. N. Y., Vol. I., p. 99, pi. xxx., fig. 9. 

 Trematis filosa, Hall; 23d Rept. State Cab., Expl. of pi. 13, flgs. 21 and 22. 

 Shell orbicular, or very slightly ovate, the beak of the upper or free 

 valve projecting a little beyond the limits of the circle, giving a some- 

 what greater diameter along the median line than in a transverse direc- 

 tion. Free valve moderately convex, the central region being the most 



