1865.] REYIEW OF THE NORTHERN BUCCINUMS. 365 



ridges, as the case may be. The difference between them is very 

 conspicuous in B. glaciale. The columella has normally three 

 folds, an upper, middle, and lower one ; — the lower one constitut- 

 ing the oblique inferior margin of the columella. These folds are not 

 always distinct, but all of them may be made out in B. temte. The 

 middle fold is obsolete in most of the species, but is very prominent 

 and tooth-like in B. ciliatum. The layers of the shell are very 

 distinct in this genus, the outer coat being most frequently of a 

 brownish color. The periostraca is generally ciliated with minute 

 processes along the lines of growth, corresponding to their inter- 

 sections with the secondary ridges. 



The operculum is oval or subcircular, and may have the nucleus 

 near the centre, or more or less approximated to the posterior 

 (outer) margin, according to the species. On the lingual ribbon 

 as in all the Buccinidae, we find three teeth in each row, the central 

 one of which is lamelliform, with denticles on its posterior edo-e ■ 

 while each lateral tooth lias two strong hook-shaped denticles, with 

 smaller ones between them. The denticles of the central tooth are 

 more numerous than in Neptunea. 



With one or two doubtful exceptions, the genus Bucdnum is 

 restricted geographically to the temperate and frigid seas of the 

 northern hemisphere. More careful examination, both of the 

 shell and soft parts of the antarctic species* referred to the °-enus 

 is required, before deciding upon their actual pertinence to it, 

 Geologically, the history of the genus commences in the Pliocene 

 formation. They are found in the European Tertiary deposits of 

 that age, even as far south as the shores of the Mediterranean, 

 They become very numerous in the Pleistocene deposits both of 

 Europe and North America, but reach their maximum develop- 

 ment in the existing seas. 



I have endeavored to include in the following review all the 

 species which certainly belong to the genus. As to the B. Dalei 

 of Sowerby, and the B. ovoides of Middendorff, if we may rely upon 

 the accuracy of the observations of Mr. Alder on the lingual den- 

 tition of the former, as detailed in Forbes and Hanley's "British 

 Mollusca," vol. iv, p. 284, these species are not true Buccinums. 

 Mr. Alder says, " Its tongue differs from that o?Buccinum undatvm 

 as well as from those of the allied species of the genus Fusus and 

 makes a slight approach to that of Mangelia. It has a single plain 



* Such as B. antarciicum and B. zealandicum. 



