16 NUCULID^. 



lunule impressly defined, its sulci finer. Interior bluish-white, the 

 front edge, in adult examples, most minutely crenulated : hinge- 

 margin broad, its teeth rather numerous on both sides. Cartilage- 

 pit small, triangular. Far. ? prod ti eta. — More elongated, ventral 

 margin less arched ; hinder side more acuminated, its tip less re- 

 curved, and more acute ; dorsal areas less pouting. 



27. L. CRASSA, Hinds, f. 69. — T. sequilateralis, ventricosa, ob- 

 longo-acuta, postice subrostrata, costa umbonali eminente et sulco 

 prof'undo lato inferne circumscripta munita, cute olivaceo-flaves- 

 ceute induta, sulcis crassis densis (quarura interslitia latiora sunt, 

 antice inclinata, postice rotundata) undique concentrice sculpta. 

 Extremitas rostri valde angusta, recurvata. Margo dorsalis antice 

 vix declivis, postice subdeclivis et profunde incurvatus ; ventralis 

 arcuatus, postice multum acclivis. Area magna, lanceolata, lon- 

 gitudinaliter Ivrata : lunula angusta, longitudinaliter striata. Jar. 

 /jrevivr. T. ovato-acuta ; margine dorsali utrinque raagis declivi. 

 — Peaked-oblong, strong; ventricose, with a curved, rounded, 

 [irominent umbonal ridge, that is cut ofr below by a broad and 

 profound groove : under a yellowish olive-coloured epidermis, 

 glossy-white (tawny when discoloured), everywhere coarsely and 

 closely grooved concentrically ; the much broader intervening lyra; 

 subimbricated in front, rounded behind. Sides very nearly equal ; 

 the front, which, if either, is the longer, with an obscure, shallow, 

 radiating indentation (which waves the sulci), rounded at its ex- 

 tremity. Posterior side quickly tapering, subrostrated ; the tip 

 of the upturned beak very narrow, higher than the middle of the 

 shell. Pront dorsal slope very slight, barely convex : hinder dor- 

 sal slope rather slight, deeply incurved. Ventral margin more or 

 less arched, not refuse, much rising posteriorly. Escutcheon 

 large, lanceolate, well dehned by the raised (and, as it were, cre- 

 nated) umbonal ridge, lyrated lengthways. Lunule narrow, per- 

 ceptible, finely grooved lengthways. Hinge-margin broad ; car- 

 tilage-pit rather small, triangular; teeth numerous on both sides. 

 Far. brevior. Peaked-ovate ; the slopes more decided. 



28. L. GIBBOSA, Sowerljy, f. 79. — T. sequilateralis, ventricosa, 

 oblongo-rostrata, cute induta, costis subarctis subrotundatis un- 

 dique sculpta. Extremitas rostri acuta, subrecurvata. Margo 

 dorsalis antice convexiusculus et vix declivis, postice declivis de- 

 mumque incurvatus ; ventralis postice siuuatus. Area magna, 

 concava, longitudinaliter lyrata, plica umbonali superne acute 

 angulari, circumscripta. Lunula inconspicua. — Beaked-oblong, 

 solid, ventricose, chalky-white under an epidermis that ranges in 



