2G0 THE mahquts de f6lin on the cjectdjt;. 



Numerous specimens of JBrochina glabra from sand dredged 

 at Belleisle and the Bay of Biscay, representing a variety {mi- 

 nima) of the species, and which are extremely transparent, resem- 

 bling the purest crystal, exhibit the same reflected border, but 

 without any appearance of tumefaction. 



The results of several dredgings on the coast of Syria and in 

 the Mediterranean have furnished further specimens in the same 

 condition. From what has been stated, we may conclude that 

 the character of the genus is reduced to this, — that the shell is 

 smooth, and that the septum is mammillated, points common 

 to the other Csecidse. Nothing remains, then, as a distinctive 

 character but the convexity of the operculum. But is this a 

 point of sufiieient importance to separate shells provided with 

 such an operculum from genera under which they might be 

 ranged for several reasons equally valid with those by which it is 

 sought to exclude them ? Is our knowledge of the operculum 

 in the Csecidse so satisfactory as to allow us to regard its con- 

 vexity as a certain distinctive character ? We do not think that 

 it is, and what we have established with regard to B. Someri 

 and B. Acherina proves that there may be some reason for the 

 doubt. 



Shells occur very closely approaching BrocMna glabra, but 

 which I think it is impossible should belong to that species. I 

 have distinguished a whole series of such Csecidse presenting sucli 

 differences from each other as to justify us in establisliing several 

 species. The form which most nearly resembles B. glabra differs 

 from that species so slightly, and the general characters are so 

 much alike in the whole series, the two species diftering only in 

 certain points, that I have deemed it possible to regard the first 

 of these species as the simplest of the series, and the connecting 

 link with B. glabra. Amongst these forms are several furnished 

 with a tumefaction, which is sometimes annular, and which, if re- 

 garded as an ornamentation, does away with the character of 

 smoothness ; and we may consequently regard these shells as be- 

 longing to the genus Ccecvm, which consequently is found to be 

 closel)' allied to BrocMna. 



The following are the diagnoses of the new species above re- 

 ferred to : — 



■ 1. C^cuMiNFiMUM (published in 'Les fonds de la Mer'). PI. VITI. 

 fig. 2. 

 Testa (quoad genus) minuta, cylindrica, arcuata, tenui, siibtrausluoida, 



