THE ANNALS '^'^'^ AND MAGAZINE OF NATURAL HISTORY. [FOURTH SERIES.] No. 10. OCTOBER 1868. XXVI. — On the Typical Value of the Lingual Dentition in the right Distribution of the Genera of Gasteropoda into Natural Groups and Families, By JoHN Denis Macdonald, M.D., F.R.S., Staff Surgeon, E.N. [Plate XVI.] Though many of the weak points of pure conchology liave been brought to light by the study of the lingual dentition of the Gasteropoda, there is yet much more to be accomplished, embracing not only the acquisition of new facts by further research, but the right use of those already in our possession. We are, even now, only sufficiently acquainted with the sub-ject to know that any system of conchology, however plausibly framed, cannot be reliable where this important test has not been brought to bear. It is nevertheless true that the import of the dental characters has been either misinterpreted or not sufficiently taken into account in some of our best works on malacology. It is scarcely to be believed, for example, that, as at present received, the greater number of the genera of the two significant families Muricidas and Buccinidai require reci-procal change of place, the truth of which position will be demonstrated as we proceed with the inquiry. Mr. Jabez Hogg, in a paper* lately read before the Micro-scopical Society, quotes a passage from Mr. S. P.Woodward's * Manual of Mollusca,' that I had already transcribed for my own purpose some eight or nine years ago ; but, as that pur-pose does not appear to be infringed upon by the tenor of Mr. Hogg's reasoning, I shall still adopt the quotation in question, as affording a good idea of the commonly received views of classification by the lingual dentition {op, cit. p. 450) : — * " On the Lingual Membrane of Mollusca, and its value in Classifica-tion," by Jabez Hogg, F.L.S. &c., published in the ^ Quarterly Journal of Microscopical Science,' No. 31, July 1868. Ann. (^ Mag. N. Hist. Ser. 4. TW. ii. 17
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