Ovibos moschata. 

 Rhinoceros tichorhinus. 

 Elephas primigenius. 

 Lemmus. 



Spermophilus citillus. 

 erythrogenoides. 



400 Geological Society: — 



Of these 19 species inhabiting- Britain before the deposition of the 

 Boulder-clay, 13 survived into Postglacial times*. 



Passing from Postglacial to Prehistoric time, the Sheep, Goat, Bos 

 longifrons, and Dog make their appearance, while the great Pachy- 

 dermata, the Cave Mammals, and nearly all the northern forms dis- 

 appear. The characteristic postglacial mommals were defined by 

 the author to be 



Paleolithic man. 

 Gulo luscus. 

 Ursus spelceus ? 



ferox. 



Felis leo. 



pardus. 



Hycena spelaa. 



The author finally discussed the question of the age of the Lower 

 Brick-earths of the Thames valley and Clacton, and indicated the 

 difficulty of proving, from Palaeontological evidence, whether they 

 are pre- or postglacial. He supposed that durihg the glacial sub- 

 mergence, the valley of the Lower Thames roughly marked the 

 coast-line of the icy sea, with a climate too cold to allow the con- 

 tinued residence of the Preglacial mammals, but which might still 

 occasionally be visited by their surviving descendants, the remains 

 of which would thus be mingled with those of Arctic immigrants. 



March 10th, 1869.— Prof. T. H. Huxley, LL.D., F.R.S., 

 President, in the Chair. 



The following commuuications were read : — 



1. "On the Origin of the Northampton Sand." By John W. 

 Judd, Esq., F.G.S., of the Geological Survey of England. 



This paper was an attempt to base on the study of a rock, both 

 in the field and the laboratory, a complete aud consistent theory of 

 the conditions of its original deposition, and of the sequence and 

 causes of its various metamorphoses. 



The Northampton Sand was described as consisting of various 

 strata, usually of an arenaceous character, which frequently pass, 

 both vertically and horizontally, into a ferruginous rock, the well- 

 known Northamptonshire ore. 



The different features presented by the formation in various 

 localities were then indicated; and the lithological, microscopical, 

 and chemical characters of its constituent rocks described at length. 



These characters were shown to point to the conclusion that the 

 beds were accumulated in a delta of one or more great rivers. 



Arguments were then adduced in opposition to the theory of the 

 formation of ironstones by direct deposition, and in favour of the 

 hypothesis that the Northamptonshire ore consisted of beds of sand 

 altered by the percolation through them of water containing carbo- 

 nate of iron. 



The cause of the redistribution of the iron in the rock was then 

 discussed ; and, in opposition to the views of Mr. Maw, who has 

 * The names of these are printed in italic. 



