MARINE MOLLUSCA OF THE UNITED STATES. 183 
6. L. unca, Gould. / 
Bost. Proc., viii. 280. 1862. 
Shell small, reddish, subequilateral, covered with profound 
ridges; anteriorly broadly rounded ; posteriorly very acute; pos- 
terior dorsal margin concave, cristate, smooth; posterior ventral 
margin sub-emarginate ; teeth 12 to 15. 
Length 8, height 6 mill. 
Frying-pan Shoals, N. C. 
I have not seen this species, and it has never been figured. 
From the description, I think it possibly identical with agufa, 
Conr. 
Subgenus YOLDIA, Moller. 
Kroyer’s Naturh. Tidsskr., iv. 91. 1882. 
Shell oblong, slightly attenuated behind, compressed, thin, 
smooth, or obliquely sculptured, with a polished epidermis; pallial 
sinus*deep. 
1. L. uimatua, Say. Fig. 497. ; 
(Nucula.) Am. Conch., t. 12, 1831. 
Shell ovate-oblong, slightly rostrated posteriorly; epidermis 
light green; beaks not prominent, subcentral; with 22 anterior 
and 18 posterior teeth. 
Animal with united siphons, the anal one translucent, the 
branchial opaque white, both fringed at the openings; edges of 
foot lobes simple.: 
Length 57.5, height 27.5 mill. 
New England (northwards), N. Car. 
The above dimensions, from specimens dredged in Portland 
Harbor, Maine, are about double the size of ordinary specimens. 
The animal is said to be very active, leaping to an astonishing 
height. . 
2. L. SAPOTILLA, Gould. Fig. 498. 
(Nucula.) Invert. Mass. 100, f. 61. 1841. 
Shell ovate-oblong, very slightly rostrated posteriorly; epi- 
dermis light yellowish-green; beaks subcentral, tumid, with a 
slight flexure under the posterior tip; teeth sixteen or eighteen on 
each side. 
Length 22.5, height 10 mill. 
New England, northwards. 
Probably only a variety of Z. limatula. 
