THE WEST AMERICAN MOLLUSKS OF THE FAMILIES RISSOELLIDAE AND SYNCERATIDAE, AND THE RIS-SOID GENUS BARLEEIA. By Paul. Bartsch, Curator, Division of Marine Invertebrates. The present paper discusses several groups of minute West Ameri-can mollusks which were sadly in need of revision. They are the family Rissoellidae, formerly known as Jeffreysiclae. The change of name is required because Jeffreysia had to give way to the prior name of Rissoella. The family Synceratidae, a new designation for the family Assimineidae, which change is also made necessary because the generic name Asshninea has to be replaced by the earlier name Syn-cera. Lastly, the Rissoid genus Barleeia has been subjected to a care-ful examination, which has yielded rather interesting results, as may be seen by an examination of the following pages. Genus RISSOELLA Gray.^ 1847. Rissoella Gray, Proceedings Zoological Society of London, p. 159. 1850. Jeffreysia Alder, in Forbes & Planley's British Mollusca, vol. 3, p. 151. Gray, at the above citation, makes the following statement : " Ris-soella, Rissoa sp. Brown. Rissoa ? glaber, Alder." Rissoa glaber Alder, therefore, is the hologenotype of Rissoella. Rissoa glaher Alder, as cited by Gray, was Alder's concept of Rissoa glabra Brown at that time, a concept wliich Alder changed later when he renamed his shell Rissoa diaphana, recognizing that it was not the Rissoa glabra oi. Brown. The genotype of Rissoella, therefore, is Rissoa diaphana Alder, which is also the genotype of the synonym Jef-freysia. Forbes and ITanley publish ^ a description of Jeifreysia, which they say was entirely furnished them by Alder. This is of sufficient interest to merit reprinting at the present time : Shell spiral, conical or subglobose, thin, transparent; aperture ovate, rounded below, with the peristome thin and entire. Operculum horny, thin, imperfectly ovate, nearly straight on one side ; not spiral, but showing faint concentric lines of growth from a lateral nucleus. It is strengthened internally, on the side next the columella of the shell, by a rib with a branch toward the center of the operculum ; from this rib rises a strong, projecting plate, set at right angles to the opercular disk. Animal with four flattish tentacles ; the upper pair moderately long, the lower pair rather shorter, and spreading out broad at the base so as to unite with the outline of the head. Eyes placed on the back of the animal, a con-siderable distance behind the tentacles. They are large and prominent. Oper-1 Trans. Tyneside Nat. Field Club, vol. 1, p. 149, 1847. -British Mollusca, vol. 3, p. 151. Proceedings U. S. National Museum, Vol. 58— No. 2331. 159
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