LAMELLIBRANCHIATA. 335 



This shell is delicate in texture, smaller, more elongate, and with beaks more 

 nearly central than P. consirida. 



Formations and localities. In the shales of the Hamilton group, in Otsego 

 county, on the shores of Cayuga, Seneca and Canandaigua lakes ; and in the 

 lower beds of the Chemung group, at Ithaca, N. Y. 



Pal^oneilo maxima. 



PLATE XLVni, riGS. 29-38. 



NveidUeg maxima, Conrad. Geol. Surv. N. Y., Ann. Rep., p. 50. 1841. 

 Tdlinat ovata. Hail. Geol. Surv. N. Y., Rep. Fourth Dist., p. 196, fig. 6. 1843. 

 PaloBoneilo ■maxima (Conrad), Hall. Prelim. Notice Lamellibranchiata, 2, p. 9. 1870. 



" " " " Pal. N. Y., vol. V, pt. 1. Plates and Explanations: PI. 48, figs. 29- 



38. 1883. 



Shell large, ovate-acute ; length one-half greater than the height ; basal margin 

 very convex in the middle, curving regularly to the anterior end, and more 

 nearly straight behind. Posterior extremity narrow and abruptly rounded, 

 or sub-truncate at the termination. Cardinal line declining rapidly on either 

 side of the beak. Anterior end somewhat narrowly rounded. 



Valves regularly convex below, becoming gibbous in the middle and above. 



Beaks anterior to the centre, prominent, small, with the apices very 

 slightly incurved. Umbonal ridge distinct, sub-angular, extending to the 

 upper side of the posterior extremity ; the furrow below is broad, obscure 

 and undefiued. 



Surface marked by fine concentric strige, which are often very obscure or 

 obsolescent. Muscular scars unknown. Hinge-line crenulate, but not prop- 

 erly represented in figs. 37 and 38 of plate xlviii. 



Three specimens measure respectively 31, 32.5 and 35 mm. in length, and 

 17, 19 and 20 mm. in height. 



This species differs from all the preceding in its more gibbous form and 

 abruptly contracted posterior end, approached only by some of the elongate 

 forms of P. constrida. Its internal characters are obscure. 



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

 Fultonham, Schoharie county, and on the shores of Cayuga lake, N. Y. 



