1881.] ' lightning' AND 'porcupine' EXPEDITIONS. 937 



rounded on each side, gently curved in front, straight at the back : 

 beah small and pointed, recurved towards the anterior side ; umbones 

 very prominent ; cartilaye-pU oval, minute, placed obliquely under 

 the beak : hinge-Une straight : hinge-plate narrow : teeth consisting 

 of only a slight lateral on the posterior side : inside glossy : scars 

 indistinct. L. 0-25, B. 0-3. 



'Porcupine' Exp. 1870 : Atl. St. 10 (a single valve and a frag- 

 ment) . 



Distribution. Bay of Biscay ('Travailleur ' Exp.), a living and 

 perfect specimen ; 733 fms. 



(/ 2. Ne^ra subtorta, G. O. Sars. 



N. subtorta, G. O. Sars, Moll. reg. arct. Norv. p. 87, t. 6. f. 6, a-e. 



'Lightning' Exp. St. 1, 3. 



'Porcupine' Exp. 1869 : St. 62. 



Distribution. Spitzbergen, Norwegian arctic Expedition, Finmark, 

 Kara Sea; 30-123 fms. 



Fossil. British North-Polar Expedition, lat. 82° 33' ; 40 ft. 



y 3. Ne^^lra sulcifera^ Jeffreys. (Plate LXX. fig. 10.) 



Shell obliquely oval, convex, thin, semitransparent, rather glossy: 

 sculpture, irregular lines of growth, v\'hich become curved striae 

 on the upper part of the anterior side ; rostrum short and broad- 

 ish, separated from the rest of tlie shell by a furrow, as if pinched 

 up : it has a single ridge or keel in the middle, extending from the 

 beak to the posterior end : colour white : epidermis fibrous : margins 

 rounded on the anterior side and in front, terminating on the posterior 

 or rostral end in a blunt curve, and sloping at the back on each side 

 of the umbo : beaTcs blunt, slightly incurved ; umbones prominent : 

 cartilage-pit forming a small narrow and oblique slit : teeth as in 

 N. truncata : inside glossy, exhibiting there the underside of the 

 furrow as a ridge : scars indistinct. L. 0-25, B. 0*35. 



'Porcupine' Exp. 1869: St. 40. 1870: Atl. 9, 13, C. Sagres, 

 27, 28. 



Distribution. Bay of Biscay ('Travailleur' Exp.); 552-G28 fms. 



This species differs from N. subtorta in being somewhat broader 

 and not twisted, and in having a blunter rostrum, which is marked 

 by a ridge in the middle and separated by a furrow from the rest 

 of the shell. The last characters serve to separate it also from 

 iV". obesa. 



^ 4. Ne^ra obesa, Loven. 



N. obesa, Lov. Ind. Moll. Scand. p. 48 ; G. O. Sars, Moll. reg. 

 arct. Norv. p. 86, t. 6. f. 4, a-c. 



' Porcupine' Exp. 1869 : St. 37 (young, living). 1870 : Atl. I, 3. 



Distribution. Spitzbergen, Norway, Skager Rack and Cattegat, 

 Azores, N.E.America, Catania?; 20-1000 fms. 



Fossil, Pliocene : Calabria ? 



* Marked with a furrow. 



