22 NXJCULID^. 



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

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

 epidermis, devoid of either an umboiial 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 wiih con- 

 spicuous, remote, ilexuously longitudinal striae 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 fine, acutangular, subccntral. 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 ret use 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. iJASUTA, Sowerhy, f. 86. — T. oblongo-acuta, postice 

 multum sensimque attenuata et subrostrata ; sequilateralis, satis 

 ventricosa, radii irapressi expers, sulcis densis longitudinaliter 

 sculpta, ad regionera solitam convexiusculam plicre umbonalis 

 repente Iffivigata. Margo dorsalis antico vix declivis, postice in- 

 curvatus et declivis. Area impressa, planulata, longitudinaliter 

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

 Peaked-oblong, more or less ventricose, but gradually compressed 

 behind, white, without anterior radiating indentation ; general 

 surface very closely grooved lengthways, so that the interstitial 

 costella; (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 rotuudately acutangular. Front 

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

 decided, incurved. Ventral margin arched and obliquely rising 

 in front, straightur and moderately rising without manifest retusion 

 behind. Escutcheon flatly impressed, moderate, sulcato-lyrated 

 leng'hways. Lunule simple, narrow, linearly defined. Hinge- 

 margin broad. Teeth moderately numerous on either side of the 

 small and broadly triangular cartilage-pit. 



38. L. Mauuitiana, Sowerbt/, f. 99. — T. ovato-rostrata (non- 

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

 teralis, ventricosa, Candida, nitidissima, undique longitudinaliter 

 arete sulcata. Eostri extremitas utrinque coarctata, angustissima. 



