42 THE VOYAGE OF H.M.S. CHALLENGER. 



and sculptured with numerous concentric, very fine, and irregular wrinkles, which, in a 

 depression that marks off the slight rostrum, turn suddenly to the right in an 

 oblique direction. The front and lower outlines are regularly curved, the latter, how- 

 ever, exhibiting a slight sinuation at the radiating depression. The fi'ont portion of the 

 dorsal edge is very short, feebly excurved, the posterior, on the contrary, being long 

 and almost rectilinear, or very slightly concave. The umbo is small, but little raised, 

 situated considerably in front of the middle, and terminates in a minute glossy vitreous 

 obtuse boss. The hinge-plate is thin, bearing immediately below the beak a minute 

 oblique ligamental jiit. The interior is glossy, with only faint muscular scars. 



Length 4|- mm., height 3^, presumed diameter of a complete specimen 2|. 



Habitat.- — Station 78, east of the Azores, in 1000 fathoms; volcanic mud. 



This species is remarkable for the smallness of the rostrum and the peculiar wrinkled 

 character of the concentric sculpture. 



NecBra circinata, Jeffreys (PL X. figs. 4-46). 



Necera circinata, Jeffreys, Ann. and Mag. Nat. Hist., 1876, ser. 4, vol xviii. p. 497. 

 Ncara circinata, Jeffreys, Proc. Zool. Soc. Lond., 1881, p. 942, pL Ixxi. fig. 6. 



Habitat. — Station 73, west of the Azores, in 1000 fathoms, volcanic mud; and at 

 Station 85, Canary Islands, in 1125 fathoms, volcanic mud (Challenger). Other localities 

 which I give on the authority of Dr. Jeffreys, all north Atlantic, lat. 56° 11' N., long. 

 37° 41' W., in 1450 fathoms ; off the west of Ireland, lat. .56° 7' N., long. 14° 19' W., in 

 630 fathoms ; west of Portugal, lat. 39° 55' N., long. 9° 56' W., in 994 fathoms ; Bay of 

 Biscay. 



The figure in the Proc. Zool. Soc. gives a fair idea of the Challenger specimens, but 

 certainly exhibits a too sudden contraction of the rostrum, consequently the sinus in the 

 ventral outline becomes too deep. The upper angle is not sufficiently sharp, and the 

 position of the umbones is too forward, being in the shells before me (when viewed in the 

 same position as the figure) exactly midway between the extremities. If these specimens 

 had not been examined by Dr. Gwyn Jeffreys, and pronounced to belong to this species, 

 I should almost have felt warranted in separating them specifically, for besides the 

 differences already alluded to, there are other points in which they do not agree with the 

 description in the Annals. There no mention is made of the position of the beaks, the 

 shell is described as " rather solid," and as having " about twenty-five fine concentric and 

 equidistant lamellar ridges or strise in the middle of the shell, which become compressed 

 in front and disappear at the sides." The Challenger shells certainly are not " rather 

 solid," but may be so in comparison with certain other species, and the concentric 

 lamellae, in a specimen of the same size as that figured by Jeffreys, are considerably more 

 numerous, there being as many as forty. Another feature which is not referred to by 



