1881.] 'lightning' AND 'porcupine' EXPEDITIONS. 941 



angular and has no distinct rostrum ; but it may have been the 

 ancestor of the recent species. 



u' 12. Ne^ra contracta', Jeffreys. (Plate LXXI. fig. 4.) 



Shell transversely oblong, convex, thin, opaque, lustreless : 

 sculpture, 25-30 riblets or raised striae in the line of growth, those 

 on the rostrum being at a right angle to the rest : the rostrum is 

 sometimes angulated and keeled : colour whitish : margins rounded 

 on the anterior side, contracted and gently curved in front, whence 

 there is a gradual slope to the snout-like rostrum ; posterior side having 

 a truncated extremity ; dorsal margin somewhat incurved : Leaks 

 small, blunt, intorted and sunken ; umboues prominent : cartilage-pit 

 narrow, oblique : hinge-line slightly curved on the anterior and nearly 

 straight on tlie posterior side : Jdnge-plate reflected anteriorly, and 

 somewhat thickened posteriorly: teeth, a single slight laminar lateral 

 on the posterior side of the right valve, parallel with the hinge-plate, 

 and extending to the upper end of the rostrum : inside glossy : 

 muscular scars large and distinct. L. 0'2, B. 0"35. 



'Porcupine' Exp. 1870: Atl. St. 16, 17, 17«. Several valves. 

 Easily distinguishable from N. lamellosa, not merely by its greater 

 size, but by its narrow or contracted shape and proportionally large 

 rostrum ; the lateral tooth also, in N. lamellosa, is triangular and 

 short, not laminar and elongated as in the present species. Another 

 species, from the ' Challenger ' Expedition, has been named coarctata 

 (coartata) by Mr. Watson. 



^ 13. Ne.era semistrigosa -, Jeffreys. (Plate LXXI. fig. 5.) 



Shell oval-oblong, convex, thin, scmitransparent, and rather 

 glossy : sculpture, 12-15 delicate concentric riblets on the posterior 

 side only ; the rostrum is closely wrinkled across ; and the rest of the 

 shell is smooth : colour clear white : margitis rounded, somewhat 

 wedge-shaped on the anterior side, gently convex in front, and 

 sloping upwards to the posterior side ; rostrum slightly upturned, 

 short and broad, defined by a shallow indentation, with a truncated 

 extremity ; dorsal margin interrupted by the umbo, raised on the 

 anterior, and nearly straight on the other side : bea/cs sunken, small, 

 and mamillar ; umbones prominent : cartilage-pit pear-shaped, 

 lying ol)liquely inider the beak : hinge-line corresponding with the 

 dorsal margin : hivge-plate thin, reflected on the anterior side : teeth, 

 a long laminar lateral on each side of the right valve, that on the 

 posterior side being triangular in the middle : inside polished : inus- 

 cular scars triangular and large. L. 0"25, B. 0"4. 



'Porcupine' Exp. 1870: Atl. St. 16, 17, 17«. 



Allied to N. notabilis ; but the shape of the present species is 

 more oval or oblong, the concentric ridges are less numerous and 

 are confined to the posterior side, the rostrum is broader and not 

 keeled and is separated by a shallow indentation, and the lateral 

 teeth are much larger. 



1 Contracted. - Half-wrinkled. 



