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17

Dall

The Pelecypoda, by William Healey Dall. [Trans. Wagner Free Inst. of Sci. Vol. 3, part III, March 1895, pp. 483-570]

The author, in 1889, in a "catalogue of the shell-bearing mollusks of the south eastern United States" proposed a new classification of the Pelecypoda. This paper is an [[crossed-out]] revision [[/crossed-out]] ^[[amplification]]^ of that work, bringing it down to the present date ^[[but]]^ conforming ^[[to]]^ the general principles on which the earlier classification was founded. In this system the shell, the anatomy, the embryology and evidence from all sources are considered and made use of. A brief dissertation on the shell anatomy, and functions, of the Pelecypoda, is given.

Then follows an enumeration of the Orders, Suborders, Superfamilies and Families of the Pelecypoda, each of which is differentially defined in a manner enabling a direct comparison to be made between groups of the same rank. Under each family is given its range in geological time and a list of the principal genera believed to bo referable to it. Some notes on the principles of nomenclature applied in the work, and an index to the genera are appended. The importance of this paper lies in the revision of the diagnostic characters, which are endeavored to be made strictly comparable in the different groups, and when common to a larger group are not repeated in the definitions of its subordinate divisions, and in the bringing up to date of the data employed.