8 NATURAL HISTORY 



Cornua Ammonis are very common about this village. As 

 we were cutting an inclining path up The Hanger, the 

 labourers found them frequently on that steep, just under the 

 soil, in the chalk, and of a considerable size. In the lane above 

 Well-head, in the way to Emshot, they abound in the bank, 

 in a darkish sort of marl ; and are usually very small and soft : 

 but in Clay 's Pond, a little farther on, at the end of the pit, 

 where the soil is dug out for manure, I have occasionally ob- 

 served them of large dimensions, perhaps fourteen or sixteen 

 inches in diameter. But as these did not consist of firm 

 stone, but were formed of a kind of terra lapidosa, or hardened 

 clay, as soon as they were exposed to the rains and frost they 

 mouldered away. These seemed as if they were a very recent 

 production. In the chalk-pit, at the north-west end of The 

 Hanger, large nautili are sometimes observed. 



In the very thickest strata of our freestone, and at consider- 

 able depths, well-diggers often find large scallops or pectines, 

 having both shells deeply striated, and ridged and furrowed 

 alternately. They are highly impregnated with, if not wholly 

 composed of, the stone of the quarry. 



LETTER IV. 



TO THE SAME. 



As in a former letter the freestone of this place has been only 

 mentioned incidentally, I shall here become more particular. 



the analogue of the cockscomb oyster, the Mytilus Crista Galli of Lin- 

 naeus and Ostrea Crista Galli of Lamarck, but belongs to an altogether 

 different species," the Ostrea carinata of the latter author. " Though 

 both are plaited species, the plaits or folds are disposed in a manner 

 altogether dissimilar in the two shells : in the cock's comb oyster they 

 are in the longitudinal direction of the shell, * * * * in the keeled oyster 

 they pass transversely on each side from a ridge which is continued along 

 the middle of a considerably produced shell." Neither is it, as Mr. 

 Bennett further remarks, a chalk fossil, but belongs to the Upper Green- 

 sand, of which the white malm of Selborne is a member. T. B.J 



