NUCCLID^. 



attenuated and subrostrated behind, rather compressed, sliining 

 white, striated lengthways throughout (except a small triangular 

 space in the lower corner of the left valve just adjacent to the 

 planulate umbonal ridge, which latter is also somewhat smoothish 

 near its termination) ; strise very close (rather less so in the front 

 of the right valve), raised and concentric in front, then shelving 

 and (at least in the left valve) more or less slanting. Dorsal edge 

 but little sloping on either side, plano-convex in front, plano- 

 retuse behind. Ventral margin much arched, rising almost 

 equally at both ends. Beaks little prominent. Escutcheon nar- 

 row, flattened, well defined by the very prominent crenulated edge 

 of the umbonal sidge. Front dorsal area less conspicuous, con- 

 centrically striated. Cartilage-pit broadly triangular, subemargi- 

 nated below, sunken. Teeth numerous, especially behind. 



8. L. CRENIPERA, Sowerhy, f. 37, 38, — T. anguste oblongo- 

 lanceolata, subsequilateralis, convexa, postice rostrata et valde 

 attenuata, undique striata : striae concentricae, densae, argutse. 

 Margo dorsalis anticus convexiusculus, vix declivis; posticus 

 retusus, declivis. Area magna, Isevis, margine crenulato plicae 

 umbonalis circumscripta. Lunula magna, planulata, plica angusta 

 marginata. — Of an elongated oblong-lanceolate form, dull white, 

 convex, concentrically striated (the lunule excepted) throughout : 

 striae for the most part extremely fine and close, less so on the 

 narrow and scarcely elevated umbonal ridge (where they become 

 shelving), and just after a narrow fold that bounds the large and 

 flattened front dorsal area. Sides nearly equal : the front ex- 

 tremity attenuated, not well rounded above, very obliquely so 

 below : the beaked hinder side much and gradually attenuated, 

 its tip nearly central, very small and subtruncated. Front dorsal 

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

 retuse. Ventral margin arched in front, retuse before the hinder tip. 

 Escutcheon large, smooth, well defined by the crenated edge of 

 the umbonal ridge. Teeth numerous, especially behind. — Judging 

 from the nuclear portion, which is somewhat remotely lamellated, 

 and by no means elongated, the fry may readily be mistaken for a 

 distinct species. 



9. L. Metcalfei, Hanley, f. 34. — T. elongata, compressa, 

 striis densis et argixtis, quae ante radium impressum anticum re- 

 niotiores sunt et lamellosse, postice autem elevate et valde obliqufe 

 fiunt, longitudinaliter corrugata. Extremitas lateris antici multum 

 brevioris supernc subangulata ; rostri postici angusta, recurvata, 

 oblique subtruncata. Margines dorsales paululum declives ; an- 



