150 MR. H. ADAMS ON NEW MOLLTJSKS. [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 ruti(a). 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 New Genus and a New Species of 

 Mollusks. By Henry Adams, F.L.S. 



Genus Bbotia, H. Adams. 



Testa fusiformis ; spira elevata, anfractibus ad angulum spinis 

 armatis, ultimo antice subrostrato ; apertura subovata, antror- 

 sum producta. 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 sub- 

 sequently referred it in his ' Otia Conchologica.' 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 Cerithiidce, and not in the Melaniidce. It forms, in my opi- 

 nion, 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.). 



