Geological facts; or, the crust of the earth, what it is, and what are its uses

by W. G. Barrett

1. NATICA CANICULATA.
2.} VENTICRULITES.
3.}
4.} ROSTELLARIA MARGINATA.
5.}
6.}
7.} CATILLUS CRISPI.
8.}

Then comes, lastly, the Chalk: that is, the white chalk, divided into lower and upper; the lower being harder and mostly without flints, and the upper characterised by layers and bands of flint, sometimes nodular, as in Cambridgeshire, and sometimes flat almost as a pancake, as in the neighbourhood of Woolwich.

Above are some of the most characteristic fossils of the Chalk. No. 1 is a pecten, or oyster, called the “five-ribbed,” or quinque costatus; No. 2 is the plagiostoma spinosa, so called on account of its spines, a shell found frequently in our chalk or lime-pits; No. 3 is the intermediate hamite (Lat. hamus, a hook), “hamites intermedius;” No. 4 is the spatangus cor-anguinum, a very common fossil echinus in the chalk; No. 5 is the ananchytes ovata, found frequently in the Brighton and Ramsgate cliffs; No. 6 is a scaphite (Gr. skaphē, a skiff or boat); and the last is our old friend the belemnite, who has survived so many of this earth’s changes, and now finds himself a contemporary of the cretaceous inhabitants of the globe.

In many respects, the Chalk presents us with remarkable anomalies: we have sand, the green sand, but unlike in colour and in texture the sand of the old and new red sandstone, where we find it compressed and hardened into solid and compact masses of stone; we have clay, argillaceous beds such as the gault, but it is not clay hard and pressed into slaty rocks, but soft and compressible; and we have carbonate of lime, the chalk constituting the calcareous beds of this formation; but where we have met with it before it has been hard and solid limestone, and marble, not pliable and soft as in the Cretaceous system; and yet apparently it is all the same material as we have found in the earlier stages of the earth’s crust—the washings, degradations, and deludations of older and harder rocks, along with the secretions and remains of organized animals that once peopled this ancient earth; thus affording us, on a large scale, another illustration of the economy observable in all the works of God.

FOSSIL FISH FROM LEWES.

Having spoken of the fossil fishes of the Chalk, we here give drawings of two procured from the neighbourhood of Lewes, the famous fossil fishing-ground of the late Dr. Mantell; and it is due to the name and memory of the Chalk historian and geologist, to inform the reader that Dr. M. was the first who succeeded, by skilful removal of the surrounding chalk, in procuring a perfect ichthyolite from the cretaceous formation of England. The British Museum is now enriched by Dr. Mantell’s collection of fossil fishes, that once so much excited the admiration of Agassiz, when he saw them at Brighton.