utrinque sculpta, in medio sublpevigata. Latus posticum con- 

 spicue breve inferne angulatum eminensque. Margo ventralis 

 crenulatus multum arcuatus, postice satis repeute acclivis. Areas 

 tlorsales tantum lineis incrementi rude corrugatpe ; lunula baud 

 definita, baud promineus. Margo cardinalis subangustus. — Ovate- 

 trigonal, subventricose (compressed wben young), clotbed with a 

 bighly polished ashy-olive epidermis, occasionally marked with 

 smoke-coloured linear rays : with concentric subpHciform corru- 

 gations and very faint radiating striae at the broader end, rather 

 less manifest ones on the narrower end ; intermediate surface 

 nearly smooth to the eye, but under the lens (the epidermis being 

 removed) marked with radiating incised lines. Lower extremity 

 of the peculiarly short hinder side angularly prominent, dorsal 

 slope abrupt. Anterior end subangulately rounded. Ventral 

 margin crenulated within, much arcuated, rather suddenly rising 

 behind. Beaks sharply prominent. Lunular area undefined, not 

 prominent, and as well as the simple, somewhat flattened front 

 dorsal region merely coarsely wrinkled by the lines of growth. 

 Hinge-margin rather narrow : teeth as in nucleus. — The N. ar- 

 gentea of Brown (Illust. Conch. G. B., p. 85, pi. 33, f. 14, 15) is 

 probably the fry of this species. 



8. N. PROXiMA, Say, f. 118, 119. — T. subtrigona, valde in- 

 fequilateralis et obliqua, latitudine longitudinem fere fequante, 

 valida, ventricosa, cute nitida olivaceo-cinerea induta, sublaevigata. 

 Latus posticum inferne baud angulatum, acclivitate conspicua 

 marginis ventralis crenati multumque arcuati obtuse excisum. 

 Margo dorsalis anticus valde decHvis, rectiusculus. Nates erosae. 

 Lunula baud prominens, sulco tenui (in adultis) circumscripta, 

 baud divaricatim insculpta. Margo cardinalis latus. — J ar. T. 

 perobliqua, cute olivacea, lunula baud circumscripta. — Subtrian- 

 gular, very oblique, nearly if not quite as broad as long, ventricose, 

 clothed with a thin glossy olivaceous ash-coloured epidermis, when 

 adult smooth except for the pliciform wrinkles of increase, which 

 are often conspicuous on the dorsal regions, and some very faint 

 radiating striae, which are most perceptible below posteriorly. 

 Ventral margin crenated, much arcuated, much rising behind, so 

 as to cut off without angularity the posterior corner. Front 

 dorsal slope straightish, produced, very decided. Beaks almost 

 terminal, peculiarly inflected, always eroded. Lunular region not 

 prominent, defined by a thin groove (in the adult only), not diver- 

 gently sculptured. Front dorsal area rather sunken. Hinge-margin 

 broad; teeth remarkably high, curved, and sharp. — Var. More 

 olive-coloured, peculiarly oljlique; lunular region undefined. — 



