REPORT ON THE LAMELLIBRANCHIATA. 



35 



NecBra, Gray. 



The number of species in this genus has very considerably increased of recent years, 

 and although they have been subdivided to some extent by A. Adams/ and arranged into 

 sections by Dr Gwyn Jeffreys,* some further revision ajjpears to be still requisite. 

 Adams' arrangement is based partly on hinge-characters and partly on external features, 

 that of Jeflreys being founded solely on differences of sculpture, the result being that 

 shells are found in the same sections with others, the hinges of which are very different, 

 e.g., Necera teres, Necera semistrigosa, Necera injiata, &c. 



Having examined a large number of species, I have found certain differences in their 

 hinges which may form the basis of a rearrangement, in submitting which, however, I at 

 present refrain from naming the sections in which I have grouped the species, awaiting 

 still further material, so that their validity and usefulness may be tested. Those species 

 whose names are marked with an asterisk (*) have been located from description only, 

 and not from personal examination. 



Section A. (Necera proper). 



Teeth. — A single more or less elongate lateral tooth on the posterior side 'in the right 

 valve, none in the left. 



Cartilage. — More or less obliquely inclined posteriorly. 

 Surface. — Concentrically striate, lamellated, or costate. 



Necera cuspidata, Olivi. 

 rostrata, Spengier. 

 obesa, Loveu. 

 suhtorta, Sars. 

 hindsiana, A. Adams. 

 rosea, Hinds. 

 circinata, Jeffreys. 

 aiocarinata, kerg uelenensis, 



plateiisis, angasi, meridi- 



onalis, consociata, azorica, 



capensis, patago7iica,wolla- 



stonii, all n. sp. 

 chinensis, Gray. 

 latisidcata, Tenison-Woods. 

 elegans, Hinds. 



Necera arcuata, Dall (?) 



Necera gracilis, Jeflfreys. 



bicarinata, Jeffreys. 

 depressa, Jeffreys. 

 limatula, Dall (?) = con- 



tracta, Jeffreys. 

 ruginosa, Jeffreys. 

 truncata, Jeffreys.' 

 arctica, Sars.'"' 

 glacialis, Sars.* 

 jugosa. Wood.* 

 papyria, Jeffreys.* 

 exigua, Jeffreys.* 

 nobilis, A. Adams.* 

 nasiita, A. Adams.* 

 trailli, Hutton.* 



* Ann. and Mag. Nat. Hist., 1864, vol. xiii. p. 206. 

 ^ Left valve only examineil. 



2 Proc. Zool. Soc. Land., 1881, p. S.^B. 



