180 NEW-YORK FAUNA — MOLLUSCA. 
NucuLa GOULDI. 
PLATE XIII. FIG, 221, a. 3. 
(STATE COLLECTION.) 
Description. Shell thin, ovate, subequilateral; the valves gape more widely at one extre- 
mity, with slightly impressed concentric strie: posterior dorsal margin slightly curved ; ante- 
rior dorsal area with a very slight central carination ; anterior margin slightly rostrate, with 
three or four imbricated strie on the sides, extending from the beaks to the margin, where the 
imbrications are most apparent; basal margin regularly rounded and entire. ‘Teeth eighteen 
in each valve, oblique, triangular, slightly directed upwards. Beaks decorticated, contiguous, 
nearly medial. Ligamentary pit profound; ligament wholly interior, black : muscular im- 
pressions distinct, oblong-oval, the posterior most profound. 
Color. Epidermis olive-green, with a few paler concentric lines, becoming still lighter 
towards the anterior extremity ; within pale bluish white, approaching to iridescence. 
Length, 0°4. ‘Transverse diameter, 0°8. 
This description was made from a single specimen obtained in Long island sound. It 
resembles myalis in its general form, but differs in the number of its teeth, in its size, and 
the conformation of its postcrior side, which is not subtriangular. I have named it after one 
of our most accurate conchologists, Dr. A. A. Gould. 
(EXTRA-LIMITAL.) 
N. myalis. (Cournovy, Bost. Jour. Vol. 2, p. 61, pl. 3, fig. 7. Px. 13, fig. 219 of these pages.) 
Shell ovate, thin, smooth, slightly gaping at both extremities: anterior side longest and rounded; 
posterior side subtriangular, acuminated and subrostrated. Teeth about twelve on each side, in- 
creasing in size and distance towards the outer extremities: surface with minute radiating strie, 
Color: epidermis olive; within glossy white. Length, 1+0; transverse diameter, 1-6. Stomachs 
of fishes. Northern Coast. 
N. limatula. (Say, Am. Conch. pl. 12. Conran, pl. 6, fig. 1. Px. 18, fig. 218 of these pages.) 
Shell elongate, subovate, smooth-polished. Beaks nearly medial, not prominent, above the curve 
of the hinge-margin, rostrated. Teeth nineteen to twenty-two on the anterior, and eighteen on 
the rostrated side. Color: epidermis light green. Length, 0+8 — 1-0; transyerse diameter, 1-9 — 
2°3. Shores of Maine and Massachusetts. 
N. sapotilla. (Gouxp, Invert. Mass. p. 100, fig. 61. Pu. 13, fig. 220 of this book.) Shell thin, 
elongate, inequilateral, subrostrated, tumid at the beaks, with a slight flexure under the posterior 
tip. Teeth about sixteen or eighteen on each side. Color, pale yellowish green. Length, 0°45; 
transverse diameter, 0°8. Fishes on the Northern Coast. 
N. navicularis. (Couruovy, Bost. Jour. Vol. 2, p. 178, pl. 4, fig. 4.) Shell small, fragile, 
crescent-shaped, inequilateral: surface smooth, rounded before, slightly truncated behind; umbones 
tumid; basal margin strongly curved. Teeth eight before and ten behind the pit. Color: epi- 
dermis light pea-green. Length, 0+5; transverse diameter, 0°25. Stomachs of fishes. 
