Nr('i;i,iD^E. 19 



pone umbones retusa, ovato-acuta, in medio latior, costellis con- 

 centricis densis (superne remotioribus) undique sculpta. Margo 

 dorsalis antice declivis, pra3cipuc rectus, ad extremitatem convexus; 

 postice subrectus; ventralis antice et in medio multum arcuatus, 

 postice multum acclivis. Arece dorsales magiife, rugis remotis 

 subobliquis liratas. Area ipsa subduplex ; interior tantum tenui- 

 ter longitudiualiter rugosa ; exterior retusa. — Peaked-ovate, ven- 

 tricose or tumid at the umboes, a retusion of surface behind 

 tlicm, -nhitish (often stained with rust-colour, when dead) ; umbo- 

 nal ridge a little convex, and detincd anteriorly by a slight radia- 

 ting indentation ; entire surface (the dorsal areas excepted) most 

 closely sculptured concentrically by riblets which lie further apart, 

 and are more conspicuous on the umboes. Sides equal, or nearly 

 so : middle region broad, quickly tapering to a rounded extremity 

 in front, and to an acute angle, whose apex is either in the middle 

 or rather above it, behind. Front dorsal slope moderate, at first 

 straight, then convex. Hinder dorsal slope nearly straight. 

 Ventral margin much arcuated in the middle and anteriorly, 

 much and somewhat straightly rising behind, devoid of manifest 

 retusion, except a slight one near its posterior end. Dorsal areas 

 large, marked with rather large, obliquely subconcentric, distant, 

 raised wrinkles, which do not extend to the middle of the bipartite, 

 well defined escutcheon, which is retusely impressed near its mar- 

 gin only, the more raised core being very finely wrinkled length- 

 ways, thus forming a series of obtuse angles. Cartilage-pit small, 

 triangular. Hinge-margin broad : the teeth rather numerous on 

 both sides. — Although the costellar intervals are simple, yet one 

 or two minute, raised, radiating lines mny in very fine specimens 

 be discerned at the commencement of the retusion which precedes 

 the posterior ridge.* 



32. L. VENTRicosA, Iluuh, f. 88, 89. — T. fequilateralis, superne 

 magis minusve tumida, anguste ovali-acuta, liris concentricis un- 

 dique sculpta. Extremitas rostri angusta. Margines dorsales 

 tantum subdeclives; anticus convexiusculus ; posticus rectiusculus. 

 Areae dorsales profunde iinpressse : area ipsa magna, rugis lamel- 

 losis inferne obliquis remotiusculis, superne longitudinalibus arc- 

 tioribusque, ornata. Lunula lineis elevatis obliquis inferno fuber- 

 culata. — Peaked oval-oblong, ventricose, tumid at the umboes, 



* Tliis is not the N. striata of Kins, ii> tlie ' Zoolofxical Journal ' (v. p. .337), who, 

 not being a concholofrist, has so described his species that it is practically undefined. 

 " T. striata, suhtumida, crassa, aubtrigona, alba ; latere antico (posticoi productiore, 

 subrostrato ; long. -^j lat. J poll." His specimen was from deep water, twenty 

 miles from the shores of Patagonia. 



