LAMELLIBRANCHIATA. 315 



NucuLA Randalli. 



PLATE XLV, FIGS. 6-10. 16, 23, 26, 27 ; and PLATE XCIll, FIGS. 1-3. 



Nucula Randalli, Hall. Prelim. Notice Lamellibrauchiata, 2, p. 3. 1870. 



In part Nttcula Handalli, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations : PI. 45, figs. 5-16. 



18S3. 

 CiicuUea opitna. Hall. Geol. Rep. Fourth Dist. N. Y., p. 197, No. 78, fig. 3, p. 196. 1843. 



Shell robust, of mediuin size ; short ovate ; length about one-third greater than 

 the height ; basal margin regularly rounded, very abruptly curving at the 

 anterior and posterior extremities ; dorsal margin sloping gradually down- 

 ward ; anterior margin abruptly declining from the beaks. 



Valves ventricose ; depth of the conjoined valves equal to the height of 

 the shell. 



Beaks at about the anterior third closely incurved. Umbo very promi- 

 nent. Post-umbonal slope abruptly rounded and extending nearly to the 

 post-cardinal extremity. 



Test comparatively thick, marked by fine, regular, angular thread-like 

 striae, which are interrupted by varices of growth, and are usually fasciculate 

 on the anterior portion of the shell ; also by extremely fine radiating striae, 

 which are usually more conspicuous below the middle of the valve, and which 

 are often obscure or entirely obsolete. 



Muscular impressions strongly marked. Teeth coarse. 



Four characteristic specimens measure respectively 25, 23, 22 and 21 mm. 

 in length; 17, 16, 15 and 15.5 mm. in height; and 18, 16.5, 14 and 12.5 

 mm. in depth. 



This species presents the general form of N. lirata, but the beaks are broader 

 and more closely incurved, and the surface is not marked by the strong undu- 

 lations which characterize that species.* 



• In the Preliminary Notice of the Lamellibranchiata, 2, page 3, the Cucullea ophna, of the Report of the 

 Fourth Geologic-al District, 1843, was eri-oneously referred to Nucula lirata of Conkad. I have recently 

 examined the original specimen of the Cueidlea opium, and there can be no hesitation regarding its identity 

 with N. Randalli, of 1870 ; but since the latter has gone into the literature of the science, I have preferred 

 to leave the name as it stands at the head of this description. 



