360 PALEONTOLOGY OF NEW YORK. 



marked by very fine, radiating, granulose striae which may be more or less 

 interrupted by the concentric undulations. 



Ligamental area deep and strong. Anterior muscular impression sub-cir- 

 cular, placed just within the anterior margin. Posterior scar large and shal- 

 low, situated about one-third the length of the sliell from the posterior 

 extremity. Pallial line simple. 



Four characteristic specimens measure respectively 52, 53, 57 and 75 mm. 

 in length, and 38, 35, 34 and 50 mm. in height. ' A specimen preserving its 

 normal form and proportions has a length of 70 mm., height 45 mm., and a 

 depth to both valves of 37 mm. 



In well-preserved specimens, this species is distinguished by the strong cinc- 

 ture with parallel furrows extending to the base. It differs from G. elliptica in 

 its more elongate form, less elevated and incurved beaks, less prominent umbo 

 and greater development of the concentric undulations. 



Formation and localities. In the arenaceous shales of the Hamilton group, in 

 Schoharie, Otsego, Madison and Onondaga counties, and rarely in the softer 

 beds of the group in Ontario aud other counties in the western part of the State. 



Grammysia nodocostata. 



PLATE LV, FIGS. 1-11; PLATE LVI, FIGS. (2, 3?) ; and PLATE LVII, FIGS. 7, 8. 



Qrammysia nodocostata. Hall. Pi-elim. Notice Lamellibranchiata, 2, j) 50. 1870. 



" " Pill N. Y., vol. V, pt. 1. Plates and Explanations: PI. 55, ti^. 1-11. 1883. 



Shkll varying from medium size to veryhirge; obliquely sub-ovoid; length 

 about one-third greater than the height; basal margin broadly curving, 

 flattened or constricted near the middle ; posterior margin abruptly rounded 

 below, and obliquely truncate above. Cardinal line straight, bordered by a 

 well-defined escutcheon. Anterior end abruptly rounded below the lunule. 



Valves regularly convex below and in the posterior portion, becoming 

 gibbous or ventricose above and in the umbonal region. Often extremely 

 gibbous from vertical compression. 



Beaks sub-anterior, prominent and strongly incurved. Owing to pressure 

 they often project beyond the anterior end. Umbo, in its upper portion. 



