REPOET ON THE LAMELLIBRANCHIATA. , 51 



which there is a peculiar pit for the reception of the anterior lateral tooth of the other 

 valve. The ligament is directed obliquely backwards, and is sustained in the left valve 

 in a small but thickish process which juts out distinct from the dorsal margin. The 

 interior is glossy, but marked with shallow radiating grooves or striae, which are even 

 more or less visible externally, owing to the transparency of the shell. The anterior scar 

 is small, the posterior rather larger, and margined on the inner side in' a strong rounded 

 ridge descending from above, under the dorsal slope. 



Length 10 mm., height 7, diameter 4f. 



Habitat. — Station VIII., oil' Gomera, Canary Islands, in 620 fathoms ; \olcanic mud. 



The shells here described have been referred by Jeffreys ^ to his Necera infiata, 

 which, however, upon examination, proves quite distinct. The form of that species is 

 somewhat difi'erent, the right valve possesses " a small upright triangular cardinal " 

 tooth, and there is "a long laminar lateral on the posterior side " in the left, both 

 of which are wanting in these specimens, which differ also in lieiug radiately lii-atc 

 upon the rostrum and in some of the hinge-characters. Smce writing the above 

 description, I have had an opportunity of examining the type of this species, and find 

 that these Challenger specimens are undoubtedly conspecific. 



Section F. 



Nemra hrazieri, n. sp. (PI. IX. figs. 3—36). 



Nemra {Rlunomya) rugata, Angas («o« A. Adams), Proc. Zool. Soc. Lund., 1867, p. 914. 



Testa parva, elongata, sublonge rostrata, iusequilateralis, mediocriter convexa, alba, 

 lamellis tenuissimis coucentricis, supra rostrum coarctatis minusque elevatis instructa. 

 Margo dorsi anticus valde declivis, leviter arcuatus, posticus concavus, elongatus. Margo 

 inferior antice et in medio arcuatus, postice baud profuude sinuatus. Eostnim augustum, 

 rotunde truncatum, bicarinatum, valvse relicpio impressione levi notatum. Umboues parvi, 

 subconici, vix involuti, antemediani. Dentes laterales valvse dextrse breves, valde erecti, 

 prope apicem coUocati. Yalva sinistra tul)erculo dentiformi, paulo ante apicem mimita. 



The shell of this species is small, rounded in front, and terminates posteriorly in a 

 moderately long and narrow beak. It is not very convex, rather inequilateral, white, 

 and not glossy. The valves are somewhat unequal in size ; the right is the smaller, 

 of a narrower appearance, and falls within the ventral margin of the left when 

 the valves are closed. They are marked posteriorly with a broad shallow depression 

 radiating from the uml)o to the ventral margin, and marking off the rostrum. The 

 sculpture consists of from twenty to thirty slender concentric lamellae, which become 

 crowded and less erect towards the depression, and upon the beak. This exhibits a faint 



> rnc. Zool Soc. Loud., ISS], ].. 94-2. 



