88 



Mr. De la Beche on the Geology of Pari of France. 



west, the other north and south; and forms large rhomboidal blocks: some few 

 groups of granite rocks on the shore are split into similar blocks, which have 

 not the same direction. 



The granite at St. Vaast and the opposite island of Tatihou * is somewhat 

 diflcrent from that of Ueville, though evidently in connection with it ; it is 

 split into similar blocks, and the fissures are in the same direction with those 

 at lleville ; in both places it is traversed by granite veins, of which the predo- 

 minant ingredient is flesh-coloured felspar. 



At high water the granite near Reville is only seen here and there, being 

 nearly covered up by sea sand ; but at low water it is more exposed to view. 

 Near Reville a little gneiss may be observed on the beach. 



Grey granite occurs at St. Honorine, a short distance S.E. from Conde sur 

 Noireau (department of Calvados) ; probably part of the same bed that is 

 found in the neighbourhood of Vire. 



In addition to the rocks already noticed in the present paper, is one which 

 ought properly to have been placed before the chalk, as it most probably belongs 

 to the tertiary formation. It occurs at Freuville, between Valognes and 

 Carentan, and consists of a tolerably hard light-coloured limestone, containing 

 an abundance of fossil shells, particularly bacculites. I observed it only at 

 one quarry near the village, and I imagine that it rests upon lias, which 

 occupies the surrounding country f . 



Another limestone, about the place of which in the series I was not alto- 

 gether satisfied, is found at Valognes : its boundaries and fossils have been 

 ably described by M. de Gerville J. It is of a light colour, contains many 

 fossils, and extends from Ivetot, in a northern direction, to St. Germain. 



At St. Laurent on the coast of Calvados there is a submarine forest upon 

 lias clay, where the remains of trees are very numerous § ; and there are also 

 traces of another on the Vaches Noires clay, between Benerville and Villers 

 sur Mer. In neither of these instances can any subsidence be discovered or 

 surmised. 



* The sands between St. Vaast and Tatihou are dry at low water, and maybe crossed on foot 

 or horseback. 



■f For a more particular account of the tertiary beds of this part of France consult M. de Ger- 

 ville's Memoirs, in the Journal de Physique (Tomes Ixxix. and lxxxiv.),in which will be found 

 very complete Catalogues of their fossils. 



X Journal de Physique, Tom. Ixxix p. 26, Catalogue G ; and Tom. Ixxxlv. p. 211, Cata- 

 logue G. 



^ Its appearance much resembles that on the north coast of Somersetshire described by 

 ,Mr, Horner. See Geological Transactions, V"ol. iii. pp. 380, &c. 



