[taylok] marine moll use a 31 



Whiteave.s gives the dimensions of a specimen dredged by Dr. Dawson 

 in Alert Bay at 12 X H X 75 mm., and I have a shell slightly larger 

 even than this.' 



According to Dr. Dall's arrangement, which we are following, the 

 suborder Naiadacea will come in here. We have two species of this 

 order, of course inhabiting fresh water, and belonging to the family 

 Unionidce. They are : 



27. Anodonta nuttalliana, Lea, 

 28. Margaritana margaritifera, Linne, sp. 



AXIN.EA, Poll. 



29. AxiN.KA SEPTENTRiONALis, Middcudorff, sp. 



Pectuncuhis septentrionalis, Midd., Mai. Ros.s., pt. Lii., p. 67, pi. xxi., fig. 1-3 (l«i9), 

 var. = A. subobsoleta, Cpr., Rept. Brit. Assoc, 186;3, p. 644 (Aug., 1864); and 

 Ann. Mag. Nat. Hist., 3rd .series, vol. xiv., p. 42.5 (Dec, 1864). 



This species does not occur in the neighbourhood of "Victoria, so far 

 as I have observed. It is found, however, not uncommonly on the 

 western and northern coasts of Vancouver Island and at the Queen 

 Charlotte Islands. (Dawson.) 



Our shell is the A. subobsoleta of Carpenter, but its specific identity 

 with the septentrionalis of Middendortf is doubted by some conchologists. 



NUCULA, Lamarck. 



30. NucDLA CASTRENSis, Hiuds. 



Froc Zool. Soc. London, 1843, p. 98; and Zool. Voy. Sulph., vol. ii., p. (W, pi. xviii.. 

 fig. 5(1844), = N. Li/alli, Baird, Proc. Zool. Soc. London, 1863, p. 71. 



This shell, which is undoubtedly the iV. Lyalli o\' Baird, and almost 

 certainly the iV. casirensis of Hinds, is the commonest bivalve shell 

 occurring in our seas. In Departure Bay last year I dredged more than 

 2,000 specimens of it in one day. Dr. Dawson dredged it at the Queen 

 Charlotte Islands and in many localities to the north of Vancouver 

 Island. 



1 Since writing the above I have had occasion to examine the description and 

 figures of the true C. fiecussafa of the Atlantic, and I find that our British Colum- 

 bian shells do not belong to that species at all. Mr. Whiteaves, in his account of 

 Dr. Dawson's collections, has twice recorded our shells as C. decusfiata, and as the 

 species had already been found on the Californian coast, I suppose we accepted his 

 determination of the shell without question. Our species may be C.faba, O. Fab., 

 but unfortunately I cannot at this moment refer to either descriptions or specimens 

 of this species. 



