NUCliMD.«. 21 



lata. JMargo dorsalis anticus vix declivis ; posticus declivis, retusus. 

 Aj'esedorsales hand detiiiitpe. — Peaked-oblong, tumid in frout,cunei- 

 formly compressed behind, scarcely, if at all, gaping, clothed with a 

 very thin polished epidermis, that ranges in tint from cinereous-yel- 

 low to yellowish-olive, quite smooth througliout, devoid of anterior 

 indented ray or nmbonal ridge. Sides equal or very nearly so ; 

 the anterior, if either, the shorter, tapering to an unsymmetrically 

 rounded extremity : the posterior gradually peaked to a narrow 

 and slightly upturned, rounded off, subcentral angle. Pront dor- 

 sal slope slight, at tirst straight, then convex, or plano-convex : 

 hinder dorsal slope moderate, retuse. Ventral margin arched, and 

 much rising in front, convex and moderately rising behind, devoid 

 of marked posterior retusion. Dorsal areas wholly undefined. 



.3.5. L. FASTiDiosA, A. Adams, f. 82, 83. — T. sequilateralis, 

 ventricosa, oblongo-acuminata, postice subcuneiformis, et vix re- 

 curvata ; cute nitidissima olivaceo-lutescente induta, superne lae- 

 vigata, inferne longitudinaliter striata; strise anticaj arctissimsp, 

 posticfe remotiores minusque conspicuce. Margo dorsalis anticus 

 leniter declivis ; posticus retusus, declivis. Area retusa, satis 

 magna, subangulatim definita, longitudinaliter lamelloso-rugosa : 

 lunula vis impressa, concentrice striata. — Acuminatcd-oblong, 

 ventricose, scarcely gaping even at the tip, clothed with a highly 

 polished yellowish-olive epidermis, devoid of either umbonal ridge 

 or indented ray, smooth on the umboes, striated lengthways be- 

 low ; the stripe very close and converging behind, fainter, more 

 remote, and concentric in front. Sides equal or very nearly so : 

 front extremity a little tapering and subangulately rounded; 

 hinder side subcuneiformly acuminated, the tip fine, scarcely up- 

 turned, below the middle. Front dorsal slope rather slight, plano- 

 convex : hinder dorsal slope decided, retuse. Ventral margin 

 arched and much rising in front, straighter and less rising behind, 

 without posterior retusion. Lunule very slightly impressed, con- 

 centrically striated, almost, if not wholly, undefined. Escutcheon 

 retuse, rather large, subangulately defined, lamellately wrinkled 

 lengthways. 



3G. L. POHTA, Sowerb//, f. 68. — T. oblongo-acuminata, sequi- 

 lateralis, ad umbones ventricosa, postice compressa, cute cinereo- 

 virescente polita induta, plicae umbonalis expers, juxta extremitatem 

 posticam lajvigatauT breviter oblique striata (in exemplis adultis in 

 medio inferne longitudinaliter remote sculpta). Margo dorsalis 

 antice vis declivis ; postice retusus, declivis. Area impressa, 

 angustc lanceolata, longitudinaliter lirata. Lunula inconspicua. 



