

22 



interesting specimens. Immediately at York, the river is only three- 

 eighths of a mile in width, but both above and below it expands to 

 a breadth six or seven times as great. 



At Wormley's creek, about two miles below the town, the cliff 

 about to be described begins ; but from this point, down to the ex- 

 tremity of the peninsula, the banks are uniformly flat and low. The 

 cliff here consists at bottom of a bluish sandy clay, containing im- 

 mense numbers of Turritella alticosta, Cytherea sayana, and many 

 small Univalves, over which lies a layer of brownish yellow sand, 

 with very few shells, and those chiefly Nucula limatula, and a few 

 other species. To this succeeds a stratum composed almost entirely 

 of Crepidula costata, so closely packed together, as to leave little 

 space for sand or other earthy matter. The whole is covered to a 

 variable depth by a stratum of coarse sand of various strong tints, 

 and evidently highly ferruginous. The elevation of the cliff in- 

 creases, and the nature of its contents gradually changes in ap- 

 proaching York. The lower stratum disappears entirely after con- 

 tinuing for something less than half a mile, previous to which, how- 

 ever, its fossil contents are changed; the layer of the Turritellae 

 being replaced by Crepidula closely packed together. Crepidula 

 still runs on horizontally above, and the intermediate stratum is now 

 densely filled with Pectens, Venus deformis, Ostrea, and a great 

 variety of small shells frequently connected together, so as to form 

 hard masses of considerable size. Still higher up the river the de- 

 posite assumes the character of successive layers composed of com- 

 minuted shells, connected together so as to form a porous rock. 

 These fragments are generally so small and so much rubbed and 

 water-worn, as to render it impossible to ascertain the species of 

 shells of which they once were portions. Many small shells, and 

 occasionally large ones, particularly Pectens, are found mingled with 

 the other constituents of the rocks; and in some places thin layers 

 of shells, such as Venus and Crepidula, intervene between the ad- 

 jacent strata. The height of this fragmentary rock amounts in 

 some places to forty feet. In most places it has a highly ferruginous 

 aspect, though this is not invariably the case. Frequently shells of 

 considerable size, such as Lucina anodonta, are seen coated with, 

 or entirely changed into, crystalline carbonate of lime, firmly ce- 

 mented in the mass. The texture of the rock is various, at some 

 points admitting of being readily excavated by the pick and spade, 

 so as to form raves which have been occasionally used by the in- 



