136 NucuLin^E. 



which is crossed by the numerous regularly disposed sublamellar 

 concentric ribs that evenly traverse the entire surface except the 

 dorsal areas, and a smooth nuclear region : their intervals, which 

 are rather broader than the ribs, unsculptured, except where a 

 few raised lines indistinctly and partially margin the broad shallow 

 rudimentary anterior indented ray. Sides nearly equal : front 

 extremity broadly and bluntly rounded ; hinder side abruptly 

 beaked, the tip very narrow, remarkably cocked-up, bluntly acu- 

 minated, above the middle. Front dorsal slope rather slight, 

 short, plano-convex ; hinder dorsal slope decided, incurved. 

 Ventral margin much arcuated in front, straighter and much 

 rising behind, retuse before its posterior termination. Lunule 

 well defined, cross-barred by riblets : escutcheon very large, ex- 

 cavated, smooth at the circumference, costellated lengthways near 

 the beaks. Hinge-margin very broad, teeth numerous, especially 

 in front. Cartilage-pit extremely minute, triangular. Epidermis 

 unknown. 



53. L. Nicobarica, Chemn. amended by Bruguiere, f. 7. — T. 

 inaequilateralis, oblonga, postice lata et superne obtuse subcunei- 

 formis, pallide fulva, striis densis subobliquis (nisi postice superne) 

 undique sculpta. Margines dorsales vix declives. Areae dorsales 

 angustae, definitse, dentes utrinque permulti. — Oblong convex or 

 subventricose, devoid of umbonal ridge, pale-tawny, closely graven 

 with obliquely concentric striae, which do not extend to the hiuder 

 triangle. Extremity of the anterior side, which occupies nearly 

 three-sevenths of the total length, unsymmetrically rounded. 

 Posterior side rather tapering, bluntly obversely subcuneiform ; 

 the extremity broad, convex, and above the middle, with a long 

 shallow dorsal notch. Dorsal slopes very slight, nearly straight. 

 Ventral margin arching up in front, then convex or subarcuated, 

 straighter behind : posterior edge oblique, somewhat convex, yet 

 a little retuse in the middle. Dorsal areas narrow, but well de- 

 fined. Cartilage-pit broadly triangular : teeth numerous on both 

 sides. — Although long known and often described, I have never 

 met with this species in good condition. The teeth seem to 

 average about eighteen on one side and twenty on the other. Of 

 the three names bestowed by Chemnitz I have preferred Nico- 

 barica, because the other two are deceptive ; for the shell is neither 

 smooth nor transparent. I doubt whether Spengler ever really 

 published his Illustrated Catalogue. 



54. L. serotina, Hinds, f. 19-21. — T. subinsequilateralis, ven- 

 tricosa, anguste oblonga, nisi superne postice sulcis remotis sub- 



