On the Division of the Sphaeriidae into Two Subfamilies: And the Description of a New Genus of Unionidae, with Descriptions of New Varieties

In, 1895, Dall called attention to the difference in, siphonal arrangement between Sphaerium and Pisidium, and said If this is found by more extensive observation to be constant within the genera the family might be divided into two subfamilies (Wagner Free Inst. Sci., III, p. 540). The examination of upward of a hundred species of these two genera, tolgether with many species of Musculiumn, s,eem to attest the accuracy of Dall's suggestion and the propriety of separation into two groups or subfamilies. Hannibal (Proc. Mal. Soc. London, X, p. 133, 1912) has instituted a family Corneocycladidae for the small clams known as Pisidium, but the name will have to be ignored since no characteristics of importance are given in the diagnosis. Subfamily SPHAERI1NAE Nov. A distinct anal and bra,nchial siphon; anterioi end ,shorter than posterior end. This group will include the genera Sphaerium, Musculium, and Eupera. Subf'amily PISIDINAE Nov. Anal siphon only developed, the branchial siphon being represented by the mantle cleft; a,nterior end longer than posterior end. This group includes the genus Pisidium. The foot of Pisidium differs from that organ in the, Sphaeriinae in being