126 NUCULID*. 



— Acuminated-oblong, more or less ventricose at the umboes, but 

 compressed behind, white under a polished, iridescent, ash-green 

 epidermis, devoid of either an utnbonal ridge or a conspicuous 

 anterior indented ray ; surface adjacent to the smooth site of the 

 former obliquely striated for a brief space, elsewhere, at most, 

 concentrically wrinkled (but in full-grown examples with con- 

 spicuous, remote, flexuously longitudinal strire in the middle, near 

 the lower edge). Sides equal or nearly so : front extremity un- 

 symmetrically rounded : hinder side gradually and remarkably 

 acuminated, the tip tine, acutangular, subcentral. Front dorsal 

 slope slight, plano-convex ; hinder dorsal slope moderate, refuse. 

 Ventral margin much rising at both ends, arched in front, convex, 

 in the middle, gradually refuse before the hinder termination. 

 Escutcheon impressed, narrow-lanceolate, lyrated lengthways. Lu- 

 nule inconspicuous, at most linearly defined and unsculptured. 

 Teeth very numerous on both sides of the small cartilage- pit. 



37. L. nasuta, Sowerhy, f. 86. — T. oblongo-acuta, postice 

 multum sensimque attenuata et subrostrata ; fequilateralis, satis 

 ventricosa, radii impressi expers, sulcis densis longitudinaliter 

 sculpta, ad regionem solitam convexiusculam plica; umbonalis 

 repente laevigata. Margo dorsalis antice vix declivis, postice in- 

 curvatus et declivis. Area impressa, planulata, longitudinaliter 

 sulco-lirata. Lunula simplex, angusta, linea circumscripta. — 

 l'eaked-oblong, more or less ventricose, but gradually compressed 

 behind, white, without anterior radiating indentation ; general 

 surface very closely grooved lengthways, so that the interstitial 

 costellse (which are about as broad as the sulci) converge behind, 

 and cease abruptly at the plano-convex site of an umbonal ridge. 

 Sides equal or very nearly so ; front extremity unsymmetrically 

 rounded, rather tapering ; hinder side subrostrated, much and 

 gradually attenuated, its tip rotundately acutangular. Front 

 dorsal slope very slight, plano-convex ; hinder dorsal slope more 

 decided, incurved. Ventral margin arched and obliquely rising 

 in front, straighter and moderately rising without manifest refusion 

 behind. Escutcheon flatly impressed, moderate, sulcato-lyraled 

 lengthways. Lunule simple, narrow, linearly defined. Hinge- 

 margin broad. Teeth moderately numerous on either side of the 

 small and broadly triangular cartilage-pit. 



38. L. Mauritiana, Sowerhy, f. 99. — T. ovato-rostrata (non- 

 nunquam angustior), postice repente attenuato-rostrata, sequila- 

 teralis, ventricosa, Candida, nitidissima, undique longitudinaliter 

 arete sulcata. Rostri extremitas utrinque coarctata, angustissima, 



