1881.] 'lightning' AND 'porcupine' EXPEDITIONS. 939 



Atl. G, 9, 13, 17, 24, 25, C. Sagres, 27-28a, 36 ; Med. Capo de 

 Gata, Cartagena B., 55, Adventure Bank, ofif Rinaldo's Chair. 



Distribution. Loffoden Is. to Shetland and the North Sea, Bay cf 

 Biscay, Mediterranean and Adriatic, New England. G. Mexico, off 

 Barbadoes ('Blake' Exp.), off Patagonia ; 10-645 fms. 



Fossil. Miocene : N.W. Germany. Pliocene : Monte Mario and 

 Sicily. 



Closely allied to iV. chinensis of Gray. According to Aradas and 

 Benoit the present species is N. ardiniana of Biondi. The animal is 

 pale yellowish-white : mantle having its edges pouting and folded 

 back : tube cylindrical, extensile, and white, I'ringed with a few 

 short cirri, which are bulbous at their extremities : foot tongue- 

 shaped, white. 



K 8. Ne^ra bicarinata', Jeffreys. (Plate LXXI. fig. 1.) 



N. bicarinata, Jeffr. in Ann. & Mag. N. H. Dec. 1876, p. 496. 



Shell slightly inequivalve, pear-shaped, somewhat compressed, 

 thin, semitransparent, and glossy : sculpture, irregular concentric 

 strife, which in a fragment of a larger specimen become wrinkles ; 

 the rostrum has two slight ridges or keels running outwards from 

 the beak, the upper being nearly parallel with the hinge-line, and 

 the lower forming with it an acute angle: colour whitish: margins 

 rounded on the anterior side, having a less degree of curvature in 

 front ; the rostrum or posterior side is defined by a shallow indenta- 

 tion ; it is broad and angular, with a blunt point ; dorsal margia 

 straight : bealx:s calyciform, incurved towards the anterior side ; 

 umbones slightly prominent : cartilage-pit small, obliquely oval : 

 hi7ige-line straight : hinge-plate thin, except under the beak : teeth, 

 a short and nearly erect lateral on the posterior side of the right 

 valve : inside glossy : inuseular scar on the posterior side triangular 

 and distinct. L. 0"3, B. 0'45. 



'Porcupine' Exp. 18/0: At!. St. 16, 17 (valves). 



Distrihuilon. North Atlantic ('Valorous ' Exp.; a fragment), Bay 

 of Biscay (' Travailleur ' Exp.) ; 690-733 fms. 



l- 9. Ne^ra TERES", Jeffreys. (Plate LXXI. fig. 2.) 



Shell triangular, convex, thin, semitransparent and glossy : 

 sculpture, smooth, with the exception of some wrinkly striae across 

 the rostrum and a ridge or keel extending diagonally from the beak 

 to the lower extremity of the rostrum ; occasionally there is a second 

 but fainter ridge, as in the last species : colour whitish : epidermis 

 thin, light yellowish-brown : margins rounded on the anterior side 

 and in front ; rostrum short, separated or defined by a slight inden- 

 tation, and ending in a somewhat truncated point ; dorsal margin 

 nearly straight : bealcs small, calyciform, incurved anteriorly; um- 

 bones prominent : cartilage-pit small, oblong, and placed obliquely : 

 hinge-line raised on the anterior, and somewhat incurved on the 

 posterior side : teeth, a short triangular lateral on each side of the 



^ Pouble-keelecl. - Kounded off. 



