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



Length 17^ mm., height 11, diameter 7^. 



Habitat. — Station 157, in the Southern Ocean south-west of Australia, at a dejith of 

 1950 fathoms; Diatom ooze. 



This species is peculiarly broadly beaked, rather swollen, and excessively thin. Since 

 this description was written the uni<|ue specimen has been accidentally smashed, only the 

 crushed fragments remaining. It is, however, probably capable of partial repair, and it 

 is fortunate that it had already left the artist's hands before it was destroyed. 



Necera Jilocarinata, n. sp. (PI. X. figs. 5-56). 



Testa elongata, antice globosa, ]50stice subanguste rostrata, tenuissima, albida, hand 

 nitida, lineis regularibus elevatis concentricis rostrum versus corrugatis sculpta. Margo 

 dorsi anticus declivis, parum arcuatus, posticus paulo concavus, obliquus ; margo inferior 

 curvatus, postice ad rostrum leviter sinuatus. Rostrum rotunde truncatum, carina 

 filiformi radianti arcuata dimidiatum, et carina alia prope marginem dorsalem instructum, 

 striis transversis corrugatus liueisque paucis radiantibus inconspicuis insculptum. 

 Umbones parvi, parum producti, paulo antemediani. Valva sinistra omnino edentula, 

 dextra dente unico laterali tenui vitrinque instructa. Ligamentum parvum, obliquum. 



This is a very thin species, rather globular, with the exception of the posterior 

 rostrated portion. It is somewhat inequilateral, whitish, wdthout gloss, sculptured with 

 very fine and rather regular concentric elevated lines which become more or less indistinct 

 and wrinkled in the faint dt'pression marking ofl' the rostrum. The front dorsal margin is 

 very faintly excurvcd and rather sloping, the hinder, on the contrary, being a little 

 concave, longer, and also oblique. The ventral is broadly excurved in front and at the 

 middle, but has a shallow siuuatiou at the depression towards the commencement of the 

 rostrum. This is roundly truncated at the end, and is divided by a distinct, slightly 

 arcuate, thread-like ridge, which radiates from the beak to the lower extremity. It also 

 exhibits a similar but rather more slender keel close under the upper margin. It is 

 sculptured by wrinkled cross hnes of gro"wi;h, and bears in addition a few inconspicuous 

 radiating lines. The umbones are not much elevated above the hinge-line, small, 

 inclined towards the front, glossy at the tip, and situated rather in advance of the centre. 

 The left valve is altogether toothless. The right has a single lamellar tooth on each 

 side, the anterior being a trifle nearer the apex than the posterior, which, however, is the 

 larger of the two. The ligament is small and inclined posteriorly. The interior is 

 shining and concentrically streaked with opaque white upon a subpellucid white ground. 



Length 9^- mm., height 5f, diameter 5. 



Ilahitat. — Station 98, off West Africa, in 1750 fathoms; Globigerina ooze. 



