LAMELLIBRANCHIATA. 465 



volume. It is distinguished by the central position of the beaks, the emargi- 

 nate posterior end and the peculiar character of the surface radii. 



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

 Schoharie county, and on the shores of Skaneateles, Otisco, Cayuga, Seneca 

 and Canandaigua lakes ; at Smyrna, Chenango county, and in other places in 

 the State of New York. 



CIMITARIA, Hall. 1870. 



CiMITARIA CORRUGATA. 



I'l.ATK LXXVII, FIGS. 1-4. 



Cj/prieardites eorrugata. Conrad. Jour. Acaii. Nat. Sd., vol. viii, p. 244, pi. 13, fig. 6. 1843. 

 Vimilaria cmiiigata (Conrad), Hall. Pi'elim. Notice Lamfllibranchiata, 2, p. 67. 1870. 



" Pal. N. Y., vol. V, pt. 1. Platos and Explanations : PI. 77, figs. 1-4. 

 1883. 



Shell large, sub-falciform, extremely elongate, with the cardinal line curving 

 upward at the extremities ; length three times the height ; basal margin 

 regularly curving, with a gentle sinuosity near the anterior end. Posterior 

 extremity vertically or somewhat obliquely truncate. Cardinal line concave, 

 essentially parallel with the basal margin. Anterior end obliquely truncate 

 above and rounded below into the basal margin. 



Valves depressed-convex in the lower and posterior portions, more convex 

 and .somewhat gibbous in the umbonal region. 



Beaks at about the anterior sixth, prominent and incurved. Umbonal 

 slope angular, marked by a distinct fold, which extends to the post-inferior 

 extremity. Post-cardinal slope comparatively wide, marked by one, or 

 several radiating folds, which are sometimes obsolescent. Cincture dis- 

 tinct, extending obliquely backward from the beak to the base, giving a 

 sinuosity to the margin. 



Surface marked by numerous fine concentric strioa. The body of the shell 

 is also marked by irregular concentric undulations, which are sometimes 

 interrupted, giving the surface a rugose appearance. The undulations ter- 

 minate upon the angular umbonal slope, the post-cardinal area being simply 



