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Show 150 MR. H. ADAMS ON NEW MOLLUSKS. [Mar. 13, one of the small ponds near the Small Mammals' House. Five eggs were laid by the female in one of the breeding-boxes about the second week in April, and five young birds were hatched on the 15th of May. One of the five died in the first downy plumage, which in this species very nearly resembles that of the young Ruddy Sheldrake (Tadorna rutila). When about three months old the remaining four moulted into the first feather-dress, in which stage they were all four alike, and nearly resembled the adult male, having the head and neck black. In the autumnal moult three of them threw off the black hood, and assumed the characteristic white head of the female. This curious change of plumage appears to me of considerable importance, as I am not aware that any previous instance has been recorded in which, the sexes being differently coloured, the dress of the immature bird resembles that of the adult male. 3. Descriptions of a N e w Genus and a N e w Species of Mollusks. By H E N R Y A D A M S , F.L.S. Genus BROTIA, H. Adams. Testa fusiformis; spira elevata, anfractibus ad angulum spinis armatis, ultimo antice subrostrato; apertura subovata, antror-sum product a. Operculum corneum, tenue, rotundatum, multi-spirale. BROTIA PAGODULA, H. Ad. Melania pagodula, Gould, Proc. Bost. Soc. Nat. Hist. ii. p. 218. Io pagodula, Gould, Otia Conch, p. 252. This singular shell, which was first described by Dr. Gould as a Melania, has much the appearance of an Io, to which genus he subsequently referred it in his ' Otia Conchologiea.' The operculum, however, which I have recently had an opportunity of examining, not only separates it from that genus, but shows its position to be in the Cerithiidar, and not in the Melaniidar. It forms, in my opinion, the type of a new group in the former family. It is from the river Thoungyin, Tavoy, Siam. COLINA GRACILIS, H. Adams. C. testa elongato-turrita, in medio tumida, tenui, pallide fulva; spira truncata, anfractibus ad 10, convexiusculis, longitudi-naliter plicatis et transverse concinne striatis,plicis in anfractu ultimo obsoletis ; sutura cingulo moniliformi ornata ; anfractu ultimo valde contracto, et in medio angulato; apertura semi-ovali, canali brevi, recurvo; columella obliqua, vix arcuata; labro valde expanso, incrassato, subreflexo. Long. 10, lat. 1^ mill. Hab. Eastern Seas (Coll. H. A.). |