MARINE MOLLUSCA OF THE UiNITED STATES. 183 



6. L. UNCA, Gould. 



Bost. Proc, viii. 280. 18G3. 



Shell small, reddish, subequilateral, covered with profomid 

 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 acuta, 

 Conr. 



Subgenus YOLDIA, Moller. 

 Kroyer's Naturli. Tidsskr., iv. 91. 1833. 



Shell oblong, slightly attenuated behind, compressed, thin, 

 smooth, or obliquelj' sculptured, with a polished epidermis; pallial 

 sinus deep. 



1. L. LiMATULA, Say. Fig. 497. 



(JSfucula.) Am. Couch., t. 13, 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 2T.5 mill. 



Wew 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. SAPOTTLLA, Gould. Fig. 498. 



(Nucula.) Invert. Mass. 100, f. Gl. 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. 



I^eio England, northwards. 



Probabl}' only a variet}- of L. limatula. 



