232 NEW-YORK FAUNA — MOLLUSCA. 
Genus Lutrarta, Lam. Shell equivalve, inequilateral, transversely oblong or rounded, gaping at 
the ends. Hinge with one tooth, which is somewhat complicated; or two teeth, of which 
one is simple, with an adjoining deltoid hollow, which is oblique and prominent within: no 
lateral teeth ; ligament internal, attached im a pit. 
L. canaliculata. (Say, Ac. Sc. Vol. 2, p. 311. Conrap, Mar. Conch. pl. 10, fig. 1. Px. 31, fig. 
298 of this work.) Transversely oval-orbicular, very thin and fragile, inflated: valves with equal 
concentric grooves; posterior margin short, subreniform, compressed; a marginal longitudinal 
irregular subimpressed line, between which and the edges the grooves become mere wrinkles; 
posterior slope nearly straight; gape considerable: anterior margin regularly curved; within 
grooved. Color, reddish white. Length, 2+1; breadth, 2*5. Seacoast, Maryland to Florida. 
L. lineata. (Savy, Ac. Sc. Vol. 2, p. 310; Conch. pl. 9. LZ. papyratia, Conrap, Conch. pl. 10, 
fig. 2.) Transversely suboval, thin: posterior gape patulous; anterior linear, and commencing 
beyond the hinge slope; valves unequally wrinkled, undulated within: anterior margin glabrous, 
and with an indented submarginal line corresponding with the exterior carinated one. Color, 
tinged with ferruginous. Length, 1+9; breadth, 2°7. Georgia and Florida. 
Genus Monracuta, Turton. Shell ovate or oblong, equivalve, inequilateral, nearly closed: hinge 
with two teeth in each valve, and a cavity between them ; lateral teeth none; ligament internal. 
M. bidentata. (Monracu, Test. Brit. pl. 26, fig. 5. Gouxp, lc. p. 59.) Shell minute, ovate tri- 
angular: surface roughened by the lines of growth; beaks pointed, and near the broader end; 
tooth on the shorter side oblique and spoon-shaped, for the reception of the ligament. Within 
faintly marked by radiating lines. Vertical axis, 0-16; transverse ditto, 0°22. Occurs in sand. 
New-Bedford harbor, Rare. 
Genus Kextiea, Turton. Shell somewhat globular, equivalve, closed: hinge with two approximate 
teeth and a remote lateral tooth in one valve, anda concave tooth and remote lateral tooth in 
the other ; ligament internal. 
K. rubra. (Turron, Conch. Ins. Brit. pl. 11, fig. 7 and 8. Govxp, fig. 33.) Shell minute, sub- 
oval, very inequilateral: beaks prominent, with a smooth elongated and deep area before them; 
palleal impression distinct, without a sinus. Color: epidermis purplish or soiled brown. Vertical 
axis, 0°13; transverse ditto, 0°18. Among the roots of seaweed. New-Bedford Harbor. 
