244 Proceedings of the Royal Physical Society. 
in which the adult plumage is assumed at the first change 
of dress. The change commences about nine months after 
birth, and extends over the two or three months following. 
This is the rule with all the Hawks and Falcons, and is 
probably true of a large number of the Buzzards, Kites, and 
Harriers. In the Hawks and Falcons substantially no 
change of colour takes place after the first moult; if the 
individual is dark in colour to begin with, it moults into 
a dark style of adult dress; if it is light when young, 
so it moults; and it is more than doubtful, in the case of 
these birds, whether any further change takes place until 
the bird passes its prime, and even then the change appears 
to affect the females only. It is quite a mistake to assume, 
for example, that a pale blue Peregrine is necessarily a very 
old bird, or that a dark plumaged one is comparatively 
young. The dark colour, or the light, is an individual 
characteristic, and quite independent of age. 
Seasonal changes of plumage, like those seen in the 
Dunlin, or in the Mallard, do not appear to have been noted 
amongst any birds of prey. Nor is there any such change 
of aspect as that produced in the Starling, the Lapwing, or 
the Linnet, by the weathering away of the feather ends, and 
the consequent exposure of a brightly coloured inner part. 
XVII. Notes on Carboniferous Lamellibranchs. By J. G. 
GOODCHILD, F.G.8., F.Z.S., H.M. Geol. Survey. 
(Read 17th February 1892.) 
Ctenodonta and Nucula. Mr Robert Etheridge, jun., 
showed some years ago that the nuculoid Lamellibranchs 
occurring in rocks of later Paleozoic age possess a distinct 
cartilage pit, and could not, therefore, be properly referred to 
Salter’s genus Ctenodonta. This observation has received 
abundant confirmation since. But Mr Etheridge considered 
that such beaked forms as Vucula attenuata, Ph., and its allies 
belonged to a different genus, which has been usually referred 
to Leda, mainly on account of its form, and of late years to 
Nuculana for the same reason. 
