■2:U 



Fig. 145. Leiorhynchus dubinm. A specimen without fold in brachial valve; doi'sal. 

 ventral, and profile views of a more strongly marked individual (from Hall). 



t^Yellty-fo^l• to twenty-six slender, i-oimded surface plica- 

 tions, of which about six are on the fold. 



A specimen from Section 7, seventeen to twenty-one feet 

 below the Encrinal limestone, appears to be of this species. 



Genus CEXTROXELLA. Billlxos. 



[Ety. : A little point] 



(lSr)9: Canadian Xaturalist and Geologist, Vol. IV., p. 131. 189::!: Pal. 

 X. Y., Vol. VIII., Pt. II., p. -265.) 



Shell plano-convex or concavo-convex, with a terebratu- 

 loid outline. The beak of the pedicle valve is acute and in- 

 curved, with a terminal foramen, which is continuous with a 

 partially-closed delthvrium. The brachial valve bears a 

 median sinus, while the center of the pedicle valve is angular, 

 the sides sloping off rapidly. The brachidium consists of two 

 Ijranches. which unite medially to a triangular plate bear- 

 ing a median ridge. 



Cextroxella iMPKEssA. Hall. (Fig. 14(5.) (Pal. N. Y., 

 Vol. IV.. p. 402, PL LXI.) 



Distinguishing Characters. — Sub-ovate outline: convex 

 angular pedicle valve, the longitudinal outline of which is 



Fig. 146. Centronella impressa. Dorsal, ventral, and profile views of a fuU-growu 

 specimen of ordinary size : interior of a brachial valve, showing the cardinal process and 

 the sti-ong callosities to which the crura are attached. 



slightly arched; beak truncated by the foramen; small 

 brachial valve, flattened or sometimes sharply depressed 

 along the center, with the front produced and curved 



