NUCUUD.E. 133 



two perfect individuals (Mus. Cuming), which I have carefully 

 compared with the larger known species from suspicion of their 

 being immature. In the larger and apparently adult one, the 

 front dorsal area is traversed by a kind of interrupted flexuous 

 continuation of the ribs : this sculpture is not perceptible on the 

 younger example. The dorsal lips protrude. 



48. L. vitrea, IfOrbigny, f. 170. — T. perparva, ovali-acuta, 

 postice repente acuminata, subsequilateralis, alba, radii impressi 

 expers, undique arete et concentrice costellata. Margo dorsalis 

 antice convexus vixque declivis ; postice declivis, rectiusculus, 

 sed demum incurvatus ; ventralis multum arcuatus, postice autem 

 rectior multumque acclivis. Area magna, concava, angulatim 

 definita, longitudinaliter larnelloso-rugosa. Lunula trausversirn 

 costellata, aliter inconspicua. Dentes magni, utrinque satis sub- 

 aequaliterque pauci. — Peaked-oval, more or less ventricose, scarcely 

 at all gaping, snow-white, glossy, not pellucid, without anterior 

 indented ray or marked umbonal ridge. General surface most 

 closely, evenly, and prominently costellated throughout ; the costal 

 interstices mere simple sulci. Sides very nearly equal : the ante- 

 rior, if either, the longer, slightly tapering to a rounded extremity : 

 posterior side quickly and simply acuminated, its tip sharp and 

 subcentral. Front dorsal slope slight, convex : hinder dorsal slope 

 decided, nearly straight, eventually incurved. Ventral margin, 

 for the most part, much arcuated, yet straightish and rising con- 

 siderably behind, without marked posterior refusion. Escutcheon 

 large, rather excavated, lamellately wrinkled lengthways, sharply 

 angulated at its circumference. Lunule transversely costellated, 

 otherwise ill-defined. Hinge-margin broad; the large teeth nearly 

 equally (and but moderately) numerous on either side of the ex- 

 tremely minute cartilage-pit. — D'Orbigny's types in our national 

 collection have been the source of this description. 



49. L. Jamaicensis, IfOrbigny, f. 173. — T. minima, subasqui- 

 lateralis, subovato-rostrata, ventricosa, radio impresso lato antico 

 plicaque umbonali angulari (retusiouem profundam sequente) con- 

 spicue ornata, uudique costellis interstitiisque latioribus concen- 

 trice rugosa. Extremitas rostri subiti valde prominens multum- 

 que acutangularis. Margo ventralis arcuatus, bisinuatus. Area 

 magna, subduplex ; superne sublongitudinaliter corrugata; infer- 

 ne concava, lamelloso-costata, carina umbonali circumscripta. — 

 Beaked-subovate, minute, ventricose, whitish, more or less glossy, 

 with a very conspicuous broad indented anterior ray and a more 

 or less carinately angular umbonal ridge preceded by a deep 



