REPORT ON THE LAMELLIBRANCHIATA. 53 



This species, on accoimt of the internal wlielf-like process l)eueatli tlie posterior dorsal 

 margin, is <;loseIy related to Xewra daviculata of Dall, and may best be recognised by 

 a comparative description. It is less globose than that sjjecics, a little narrower, more 

 broadly rostrate behind, the ventral margin being regularly (mrved, and without a 

 shallow posterior sinuation, and the dorsal outline, behind the beak, scarcely at all 

 incurved. The umbones are placed more forward than in Xeaixi daviculata, and do 

 not curve over so much towards the posterior end. Within I find two differences. In 

 the fir.st place the " clavicle " is longer, and commences at the upjier end under the 

 dorsal margin, whilst in Ball's species the inner margin of the clavicle is joined al)0ve to 

 the process which receives the internal hinge-cartilage. The second distinction consists 

 in the narrower character of this process, which also is almost parallel witli the hinder 

 dorsal edge, whilst in Necera daviculata it juts farther out into the shell. 



Length 4 mm., height 2f, presumed diameter 2^. 



Ilahitat. — Station 33, otf Bermuda, in 435 fathoms ; coral mud. 



Only a single left valve is. at present known of this species, and that probal)ly not 

 full grown. Were there no other diflerence except that of form I should have hesitated 

 to have separated it from Necera daviculata ; seeing, however, that the clavi('le and 

 hinge are also dissimilar, I have no doubt of this being a distinct species. It is 

 unfortunate that no right valve is at hand for examination, for most likely a modification 

 of the peculiar sul)hooked tooth, met with in the allied form, would occur in this 

 species. I am exceedingly sorry to have to record the complete destrviction, through the 

 (;arelessness of a servant, of this particularly interesting valve since it was returned to me 

 by the artist. 



Section M. 

 Necera frag ilissima, n. sp. (PI. IX. figs. l-l/>). 



Testa magna, tenuissima, ovata, postice Ijreviter rostrata, globosa, hand nitida, alba, 

 ina3i|uilateralis, liris radiantiljus tenuibus instructa, incremeutique lineis striata, 

 ^largo dorsi auticus altus, supra umbones productus, posticus paulo excavatus. Latus 

 anticum superne obliquum, parum arcuatum, ad extremitatem subacute rotundatum. 

 3Iargo ventralis late curvatus, postice sub rostro leviter sinuatus. Rostrum breve, 

 liris radiantibus obsoletis ornatum, superne pone umbones aream angustam impressam 

 exhibens. Umbones postmediani, ad apicem acuti, paulo supra marginem product!. 

 Yalva dextra postice vix dentata. Pagina interna parum nitida, radiatim sulcata 

 et striata. 



This species is excessively fivagile, rather large and inflated, inequilateral, ovate- 

 rostrate, not glossy exteriorly, white, and sculptured with numerous fine radiating 



