120 NUCUL1MC. 



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. ? product 'a. — 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. aequilateralis, ventricosa, ob- 

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

 profundo lato inferne circumscripta munita, cute olivaceo-flaves- 

 cente induta, sulcis crassis densis (quarum interstitia latiora sunt, 

 antice inclinata, postice rotundata) undique concentrice sculpta. 

 Extremitas rostri valde angusta, recurvata. Margo dorsalis antice 

 vix declivis, postice subdeclivis et profundi incurvatus ; ventralis 

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

 gitudinaliter lyrata : lunula angusta, longitudinaliter striata. Far. 

 brevior. T. ovato-acuta ; margine dorsali utrinque rnagis declivi. 

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

 prominent umbonal ridge, that is cut off 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 lyrre 

 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. Yentral margin more or 

 less arched, not refuse, much rising posteriorly. Escutcheon 

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

 mated) 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, Sowerbij, 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 sinuatus. Area magna, 

 concava, longitudinaliter lyrata, plica umbonali superne acute 

 angulan, circumscripta. Lunula incouspicua. — Beaked-oblong, 

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



