LAMELLIBRANCHIATA. 297 



Test of moderate thickness, marked by regular, prominent, lamellose striae. 



Anterior muscular impression strong, sub-circular. Inter-pallial area pus- 

 tulose in the cast. Hinge thickened, carrying a single cardinal fold. Liga- 

 ment extending about half the length of the cardinal line, strong and prom- 

 inent, frequently preserved in specimens retaining the valves in conjunction. 



The striated area, anterior to the cardinal pit (fig. 19, plate xliii), does not 

 appear to be an organic feature of the hinge, but is probably due to the 

 infolding and impression of the surface strias. The hinge does not preserve 

 striae posterior to the beak, as shown in the figure. 



Three chariicteristic specimens measure respectively 87, 82 and 38 mm. in 

 length, and 39, 36 and 18 mm. in height. The smallest individual observed 

 has a length of 10.5 mm. and a height of about 5 mm. 



This species differs from G. rugosa in having the umbonal ridge more direct, 

 more prominent and strongly angular ; the anterior end is shorter and narrower, 

 the posterior extremity more distinctly truncate and the surface of the shell is 

 less rugose. 



Formation and localities. In the shales of the Hamilton group, Fultonham 

 and Bear's gulf, Schoharie county, and throughout the eastern and central 

 portions of the State. 



GONIOPHORA BUGOSA. 



PLATE XLU, FIGS. 7,8a; and PLATE XLIII, FIGS. 4-7. 



Cyprleardites rugosa, Conrad. Geol. Sui-v. N. Y., Ann. Rep., p. 53. 1841. 

 8anffuinolite» rugotus (Cohrad), Hall. Prelim. Notice Lamellibranchiata, 2, p. 37. 1870. 

 Qoniophora rugom, Conbad. S. A. Millkr. Cat. Amei'. Pal. Foss., p. 192. 1877. 



.< •• " Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 43, figs. 4-7. 



1883. 



Shell of medium or large size, sub-rhomboidal ; length less than twice the 

 height ; basal margin gently curved, flattened on approaching the anterior ; 

 posterior margin sub-truncate, gently curving from the post-basal extremity 

 to the cardinal line. Anterior end declining rapidly from the beaks and 

 abruptly rounded below. Cardinal line gently arcuate, slightly oblique, 

 extending for about two-thirds the length of the shell. 



