118 NUCULID.E. 



off acute. (Front dorsal slope nearly straight, slight : hinder 

 dorsal slope rather slight, subretuse, emarginated eventually. 

 Ventral margin subarcuated, much rising at both ends. Es- 

 cutcheon plano-concave, corrugately lyrated across, flanked by a 

 deep groove. Lunule concave, lanceolate, in the adult obscurely 

 barred like the lunule, in the young finely wrinkled concentrically. 



23. L. bicuspidata, Gould, f. 73. — T. insequilateralis, anguste 

 ovato-oblonga ; postice attenuata, biangulata, bicuspidata ; ven- 

 tricosa, eburnea, oblique striata ; ad extremitatem anticam plicis 

 angustis circiter 3 radiata. Regio postica superior exeavata, inter 

 carinas 3 serratas (quarum 2 sunt dorsales) laevigata. Margo 

 dorsalis anticus convexus, declivis ; posticus leniter declivis. Area 

 lanceolata, sublsevigata. Lunula inconspicua. — Produced ovate- 

 oblong, a little subcylindraceous, more or less ventricose, ivory- 

 white, with about 3 narrow, close, prominent folds at the extreme 

 front, and a posterior triangle, composed of a broad, smooth con- 

 cavity, flanked by serrated keels (two approximate ones above, and 

 one below), the ends of the two larger of which form two pro- 

 jecting points: surface elsewhere finely graven by numerous wavy, 

 downwards-slanting, incised lines, whose intervals rise at the 

 umbonal region into raised strioe. Extremity of the anterior side, 

 which occupies about two-fifths of the total length, rounded : 

 extremity of the attenuated posterior side biangular, deeply 

 notched. Front dorsal slope moderate, convex : hin ier dorsal 

 slight, straight, or subretuse. Ventral margin arched in front, 

 straighter behind. Escutcheon lanceolate, smoothish. Lunule 

 inconspicuous. Teeth more numerous behind. 



24. L. rostrata, Montagu, f. 84. — T. oblongo-rostrata, sub- 

 sequilateralis, eburnea, striis arctis longitudinalibus et postice 

 arcuato-obliquis undatim sulcata. Eegio postica superior lyris 

 radiantibus approximatis, interne circumscripta. Rostri extreraitas 

 angusta, recurvata. Margo dorsalis antice vix declivis, postice 

 declivis et profundi 1 incurvatus ; ventralis valde arcuatus. Area 

 magna, longitudinaliter sulco-striata. Lunula inconspicua. — 

 Beaked-oblong, subventricose, the ordinary site of an umbonal 

 ridge occupied by a kind of lattice-work formed by several ra- 

 diating linear keels and rather distant, transverse, raised striae ; 

 ivory-white (sometimes very pale tawny), rather glossy, everywhere 

 (dorsal areas excepted) waved with flexuous, closely disposed, 

 subimbricating sulci, wliich, concentric at the nucleus, and some- 

 what so in front, become arched and slanting posteriorwards. Sides 

 very nearly equal : front extremity very uns\ mmetrically rounded : 



