Abstract

IN the Proc. Zool. Soc. Lond. for May, 1881, pp. 558–561 Mr. Edgar A. Smith has described two new species of shell from Lake Tanganyika, Africa, for which he has proposed the new generic name of Paramelania. These forms are, without doubt, generically identical with the Pyrgulifera humerosa of Meek (see U.S. Geol. Sur. 40th Parallel, by Clarence King, vol. iv. p. 176, pi. xvii. Figs. 19 and 19a), which antedates Mr. Smith's name by at least five years. Mr. Meek's species has hitherto been the only known member of the genus, either fossil or recent, and was only known to occur in the strata of the Laramie group, an extensive brackish water formation in Western North America, which holds a transitional position between the Mesozoic and Cenozoic series. Associated with Pyrgulifera humerosa, among various other fresh and brackish water forms, is one that I have described under the name of Goniobasis cleburni, which is evidently congeneric with the Melania (Sermyla) admirabilis of Smith, an associate of Pyrgulifera damoni and P. crassigranulata in Lake Tanganyika. As that lake has evidently once been a brackish water sea, it is not strange that there should be certain similarities between its molluscan fauna and the faunæ of similar bodies of water that existed in Mesozoic and Cenozoic time. It is, however, remark able that the two generic types here especially referred to should appear in their integrity living in Africa, and not in North America, where the fossil forms occur; and especially so because so many of the fresh-water and land-molluscan types now living on the latter continent are found fossil in its Mesozoic and Cenozoic strata.