146 NUCULlDvE. 



what iridescent epidermis, everywhere smooth, except for the 

 wrinkles of increase or more distant furrows of growth. Anterior 

 side rather the shorter, a little narrowed and subangulately rounded 

 at its extremity, its dorsal slope straightish or plano-convex : pos- 

 terior side rotundately peaked, its tip, which is somewhat disposed 

 to turn up, in or below the middle, its dorsal slope, which is the 

 more decided one, straightish or refuse. Hinge-margin broad; 

 teeth large, about twelve ou each side of the minute triangular 

 cartilage-pit. 



71. L. hetusa, Hinds, f. 28, 29. — T. perparva, valida, rnagis 

 minusve ventricosa, vix hians, aequilateralis, postice rotundato- 

 acuminata, lsevis (nisi antice inferne), cute nitida subolivaceo-flava 

 induta. Margo dorsalis posticus leviter declivis, magis minusve, 

 retusus; ventralis arcuatus, utrinque multum acclivis. Nates 

 eminentes. Area? dorsales baud definitse. — Very small, more or 

 less ventricose, scarcely if at all gaping at either end, under a 

 subolivaceous-yellow epidermis, polished ivory-white, devoid of 

 indeuted ray or umbonal ridge, smooth, except at the extreme 

 lower anterior extremity, where the surface is graven with a few 

 distant shelving and somewhat slanting longitudinal scratches. 

 Sides equal or very nearly so : front extremity subangulately 

 rounded, tapering ; hinder side rotundately peaked, its tip rather 

 above than below the middle, a little upturned. Front dorsal 

 slope moderate or rather slight, somewhat convex, straighter near 

 the prominent beaks : hinder dorsal slope slight, more or less re- 

 tuse. Ventral margin arcuated, much rising at both ends, rather 

 more so behind, without posterior retusion. Dorsal areas wholly 

 undefined. Hinge-margin very broad. Teeth rather, and nearly 

 equally, numerous on either side of the minute shelving triangular 

 cartilage-pit. 



72. L. abyssicola, Torell, f. 167. — T. ventricosa, lsevis, an- 

 guste oblonga, cute polita olivaceo-flavente induta. Extremitas 

 lateris postici longioris sensimque attenuati satis angusta, sed 

 rotundata ; margo ejus dorsalis prope umbones tumidos promi- 

 nentes rectus et subhorizontalis. Margo ventralis arcuatus, baud 

 sinuatus. Areas dorsales haud definitse. — Narrow-oblong, ventri- 

 cose, scarcely gaping, with a shining olivaceous-yellow epidermis, 

 smooth except for the wrinkles of growth, devoid of umbonal 

 ridge or defined dorsal areas. Anterior side much the shorter 

 (about two-fifths of the entire length), its extremity well rounded. 

 Posterior side gradually attenuated to a rather narrow but well 

 rounded tip : its dorsal edge straightish and subhorizontal near 



