LAM EL LIB RAN CHI A TA. 
317 
This species is readily distinguished from any of the associated species by the 
strongly lirate surface. It differs also from N. Randall i in its surface striae, 
lesser gibbosity and more distant beaks. 
Formation and localities. In the shales of the Hamilton group, on the shores 
of Skaneateles, Cayuga and Seneca lakes, N. Y. 
Nucula subelliptica. 
PLATE XI.Y, FIG. 28. 
Nucula subelliptica, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 45, fig-. 2S. 1883. 
Shell large, ovate, wider behind; length about one-fourth greater than the 
height; basal margin regularly rounded, abruptly curving into the anterior 
end. Posterior end rounded. Cardinal line slightly arcuate. Anterior end 
short and abruptly rounded. 
Valves convex, gibbous in the middle and on the nmbonal region. 
Beaks sub-anterior, prominent, rising above the hinge-line. Umbo gib¬ 
bous. Umbonal slope rounded, becoming obsolete before reaching the post- 
basal extremity. 
Test and surface markings not observed. 
The specimen is a cast of the interior, showing strong muscular scars and 
the remains of very numerous and small post-cardinal teeth. 
The internal mould has a length of 27 mm., and a height of 20 mm., with 
a depth to both valves of about 15 mm. 
This species is distinguished from others of the horizon of the Hamilton 
group, in its regular ovate form, which is broader behind, and by its rounded 
umbonal slope. It somewhat resembles certain forms of N. bellistriata, but it is 
a larger shell, more elongate in outline, with more prominent beaks and more 
numerous hinge-teeth. 
Formation and locality. In the shales of the Hamilton group, near Cumber¬ 
land, Md. 
41 
