84 PALAEONTOLOGY OF NEW YORK. 



The specimens are casts of the interior preserved in coarse sandstone; the 

 surface markings are consequently obliterated. 



Formation and locality. In a coarse sandstone of the Chemung group near 

 Olean, Alleghany county, N. Y. 



Crenipecten obsoletus. 



PLATE IX. BIGS. 19, SI. 



Lima) obsoleta. Hail. Geolog. Surv. N. Y. : Rep. Fourth Hist., p. 265. 1843 



Crtnipecten obsoletus. Hall. Pal. N. Y., vol. v, jit. 1. Plates and Explanations: PI. 9. BgB. 19, 21. 



Jan., 1883. 



Shell small, obliquely sub-ovate, length nearly equal to the height ; margins 

 regularly curved, becoming produced on the post-basal side, and somewhat 

 recti linear on the posterior side. 



Valves very similar. Right valve depressed-convex. Left valve regularly 

 convex. 



Hinge-line straight, a little more than one-half the length of the shell. 



Beak obtuse, more prominent on the left valve; situated in the centre of 

 the hinge. Umbonal region well defined in the left valve; depressed and 

 undefined in the right valve. 



Ears small, triangular, sub-equal, defined by shallow sulci; margins gently 

 concave; extremities obtuse. Posterior ear a little the larger. Byssal sinus 

 not conspicuous. 



Test thin, marked by fine, closely arranged, concentric stria 1 , which are 

 crowded and stronger on the ears. No radiating stria 1 have been discovered. 



Ligamental area narrow, marked by a row of minute cartilage-pits. 



A left valve measures 18 mm. in length, 20 mm. in height, hinge-line 10 

 mm. A similar right valve is 16 mm. in length, 17 mm. in height, hinge- 

 line 8.5 nun. 



This species bears some resemblance to C. crenulatus, but is more elongate- 

 ovate; less oblique, with the height somewhat greater than length. 



Formation and localih/. In shales of the Chemung group at Philipsburg, 

 Alleghany county , N. V. 



