248 EMARGINULA. 



angles to the longitudinals with a series of threadlets, very similar 

 in form, but rather more closely set ; these radiate from the apex 

 and indicate the old mouth edges. Color porcellanous-white, which 

 is dead on the threadlets but almost translucent elsewhere from the 

 extreme thinness of the shell. Apex : at the posterior end of the 

 shell there is a narrow, rounded, prominent beak, within which, a 

 little bent to the right and projecting slightly above the margin of 

 the mouth, is the minute apex of one whorl. Mouth oblong. Mar- 

 gin minutely denticulated by the ends of the ribs ; cleft in front by 

 a strong, parallel-sided, blunt-ended fissure; behind, it is peculiarly 

 patulous, being markedly bont outwards from the line of attach- 

 ment of the septum, this bending being strongly shown on the out- 

 side of the shell. Inside glossy, smooth ; a strong depression corre- 

 sponding to the exterior keel extends from end to end of the shell. 

 Septum : A little way within the margin, and deepest at the end, is 

 the short oblique septum, which is faintly arched, with a concave 

 edge in front. Length O'oS, breadth 0'2, alt. 0'12inch. (Wat*on.) 

 The present species, though somewhat chipped, is of great beauty. 

 It differs from Z. calceolma which is rudely cancellated, and is also 

 wider and more depressed. It is like Z. reticulata ; but is larger 

 and deeper, has the old cleft-scar raised on a projecting ridge which 

 forms a strong internal furrow, has the beak sharper and more pro- 

 jecting, the form is more oblong and more pinched-in at the sides, 

 the sculpture lines are much finer and less regular than in that spe- 

 cies. ( Watson.) 



North of Oulebra Id., West Indies, 390 fms. 



Z. naufraga WATS , Journ. L. Soc. xvii, p. 27 ; Challenger Gas- 

 trop., p. 36, t. 4, f. 3. 



Genus EMARGINULA Lamarck, 1801. 



Emarginula LAM. Systeme des Anim. etc., p. 69 ; An. s. Vert, vi, 

 p. 212. Semperia CROSSE, Journ. de Conchyl. 1867, p. 74. 



Shell oval, obliquely conical, the recurved apex directed back- 

 ward ; front slope with either a deep incision in the margin (Emar- 

 ginula s. s.) or a closed hole (Rimula). A distinct anal fascicle 

 extends upward from the fissure, sculptured differently from the 

 other ribs of the surface ; surface latticed ; no septum or deck 

 inside. 



