LAMELLIBRANCHIATA. 467 



The surface of the anterior and middle portions of the shell is minutely pus- 

 tulose and marked by extremely fine radiating striae, which extend obliquely 

 backward from the beak. 



Three specimens measure respectively 43, 50 and 52 mm. in length, and 

 17, 19 and 22 mm. in height. 



This species is distinguished by its straight cardinal line and the gentle curva- 

 ture of the basal margin, and by the fact that the umljonal ridge extends to the 

 posterior extremity at about the middle of its height, while in the other species 

 it extends to the post-inferior extremity. 



Formation and localities. In the Hamilton group at Pratt's falls, Onondaga 

 county, and in Schoharie county, N. Y. 



CiMITARIA RECURVA. 



• PLATE LXXVir, FIGS. O-U, 16. 



Cjtpricardites remirva, Cokrad. Jour. Arail. Nat. Sc.i., Pliila., vol. viii, p. 24.'), ]>!. IS, tig-. 18. 1842. 

 Plerium pnmtuJata, Cosrad. Gool. Surv. N. Y., Ann. Rep., p. 116. 1838. 

 CyprU-ardites reaii-va, Vani'XKM. Geol. Sui-v. N. V., Rep. Third Dist., pp. 152-3. 1842. 

 dmUaria recurva (Cokrad), Hall. Prelim. Notice Lamellibrtinchiata, 2, p. t>8. 1870. 

 In part " " " " Pal. N. Y., vol. v, pt. 1. Plates and Explanation.s : PI. 77, figs. 9-1(5. 



1883. 



Shell large, falcate ; length nearly three times the height. Basal margin 

 broadly curving with a slight sinuosity toward the anterior end. Posterior 

 extremity broadly rounded or sub-truncate. Cardinal line long, concave. 

 Anterior end short, broadly rounded, obliquely truncated above by the lunule. 

 Escutcheon large. Lunule long and abruptly limited. 



Valves depressed-convex in the basal and posterior portions, becoming 

 gib))Ous above and in the umbonal region. 



Beaks sul)-anterior, prominent, appressed and closely incurved. Umbonal 

 slope obtusely angular, curving downward and becoming obsolescent before 

 reaching the post-inferior extremity. Post-cardinal slope broad, flattened or 

 slightly concave. Cincture an undefined flattening or depression, extending 

 from the beak obliquely backward to the base, and producing a slight sinuos- 

 ity in the margin. 



