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 



