464 PALEONTOLOGY OF NEW YORK. 



TELLINOPSIS, Hall. 1870. 

 Tellinopsis scbemarginata.* 



PLATK LXXVI, FIGS. 21-31. 



NiicvJites .tiiheittaiylnaia, Cosrad. Jour. Acatl. Nat. Sci., Phila., vol. viii, p. 240, pi. 15, fig-. .'5. 1842. 

 Teilhtopsix mibvmargiiuUa (Conk.id), Hall. Pi-elim. Notice Lamellibranchiata, 2, p. 80. 1870. 



" " Pal. N. Y., vol. V, pt. 1. Plates and Explanations: PI. 7G, 



figs. 21-31. 1883. 



Shell large, elliptical, sub-quadrate ; length more than once and a half the 

 height. Biisal margin straight or gently curving. Posterior extremity sub- 

 emarginate in the middle and rounded above and below, sometimes truncate 

 or rounded with no emargination. Cardinal line gently arcuate. Anterior 

 end regularly rounded, large, usually equaling or greater than the posterior 

 half of the shell. 



Valves moderately convex below and toward the extremities, becoming 

 gibbous in the middle and umbonal region. 



Beaks sub-central, rather prominent, elevated above the hinge-line and 

 incurved. Umbonal slope rounded, distinct, defined above by a depression 

 which is sometimes a furrow extending from the beak to the middle of the 

 posterior margin or below, producing a slight emargination. The post-cardi- 

 nal slope above the depression is convex. 



Surfiice marked by fine concentric striae, which are sometimes fascicled, 

 producing undulations of the surface, and also by radiating striae which are 

 more or less distinct. From the anterior side of the umbo there extends a 

 flattened space, limited on each side by a low ridge, extending to the antero- 

 basal margin, producing an undulation in the direction of concentric striae. 



Five specimens measure respectively 20, 26, 28, 31 and 49 mm. in length, 

 and 12, 16, 16, 19 and 28 mm. in height. 



This species has apparently no relation with any other form described in this 



*A weIl-marke<J Bj«»(;im('n of this sp(>(ncR in tho author's collection beai'S the following label in Mr. Con- 

 rad's handwriting: " Posidonia lelliTundfXfConRiv. Outline fig., p. 1." The reference is to a plate of outline 

 figures never published, and the writer has not found the name i-ecoiiled in any publication of Mr. Cokrad. 



