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



faintly curved and rather oblique, the posterior, which is somewhat longer, being, on the 

 contrary, considerably concave. The valves are all but equal, and sculptured with 

 numerous oblique, wavy, slender ridges, which almost disappear in front, leaving a com- 

 paratively smooth lunular space, and vanish posteriorly at a fine radiating keel which 

 bisects the rostrum. The latter bears nearer the dorsal edge a second carina, which, being 

 slightly curved, marks oS' a smooth narrow dorsal area, the space between the ridges 

 being, on the contrary, marked with rather rough transverse lines of growth, these on the 

 rest of the valve, being concentric, cut across the oblique riblets. The cartilage-process 

 is small, short, and inclined slightly posteriorly. The right valve has a thin elongate 

 hinder lateral tooth. 



NecBra sp. 



Habitat. — Station 23, ofi' Sombrero Island, West Indies, iu 450 fathoms ; Pteropod 

 ooze. 



Only the umbonal portion of a right valve was obtained, wliicli, on account of its 

 large size, may be wortli recording. It indicates a species of as large size as Netera 

 chinensis, Gray, and equally solid. It evidently has a long slender rostrum, and is 

 sculptured like Necera rostrata, Spengler. It has a trigonal cartilage-pit having the 

 lower margin rounded and placed almost perpendicularly under the tip of the beak. 

 There is a very strong short erect hinder lateral tooth, immediately beneath which is a 

 very deep muscular scar. 



NecBra sp. 



Habitat. — Station 24, oil' Culebra Island, West Indies, in 390 fathoms; Pteropod ooze. 



A single left valve from the above Station is apparently distinct from all the 

 numerous known species of this genus. It is very thin, probably young, pellucid, 

 moderately convex, shortly rostrate, glossy, and sculptured with fine lines of growth 

 towards the lower outline. The hinge-line is almost horizontal, very slightly excurved 

 anteriorly, and very feebly concave behind. The anterior end is broadly rounded, and 

 joins the dorsal margin with a rounded angle. The lower outline is well curved, rising 

 considerably at the posterior end, Avhere it is also shallowly sinuated. The Ijeak, 

 di\ided by a slight ridge radiating from the umbo to the lower corner, exhibits one or two 

 other very faint raised radiating lines, and is rather abruptly truncated. The umbo is 

 small, .shining, only a little elevated, and placed a trifle in front of the centre. The 

 cartilage-j)it is very small, oblique, and just under the apex. 



Having but a single valve for examination, and that probably immature, it would be 

 unwise to name it specifically; however, the record of its existence may possess some value. 



