LAMELLIBRANCHIA TA. 
315 
Nucula Randalli. 
PLATE XLV, FIGS. 6-10, 16, 23, 26, 27; AND PLATE XCIII, FIGS. 1-3. 
Nucula Randalli, Hall. Prelim. Notice Lamellibranchiata, 2, p. 3. 1870. 
In part Nucula Randalli, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 45, figs. 5-16. 
1883. 
Cucullea opima, Hall. Geol. Rep. Fourth Dist. N. Y., p. 197, No. 78, fig. 3, p. 196. 1843. 
Shell robust, of medium 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 opima, of the Report of the 
Fourth Geological District, 1843, was erroneously referred to Nucula lirata of Conrad. I have recently 
examined the original specimen of the Cucullea opima, 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. 
