HANDBOOK OF FOSSILS. 



Si 



clay contains plenty of fossils, only as they are disposed in layers 

 (zones} at a considerable distance apart, they are not often hit 

 upon. Layers of Septaria or cement-stones are of. frequent 

 occurrence. Sheppy is the great locality for London clay fossils, 

 as the sea annually washes down large masses of the cliffs and 

 breaks them up on the beach. A great many 

 fossil fruits and seeds, remains of crabs, shells 

 of Nautili, Volutes, and other mollusca, besides 

 turtles, a species of snake, a bird with teeth, 

 and a tapir-like animal, have at different times 

 and in various places been found in this de- 

 posit, which sometimes attains a thickness of 

 over 400 ft. The " Bognor Rock " is a local 

 variety of the basement bed of this formation. 



The MESOZOIC or SECONDARY rocks em- 

 brace a series of limestone, clays, sands, and 

 sandstones that on the whole are well con- 

 solidated. The main mass of them lies to the 

 west of a line drawn across the map of Eng- 

 land from the mouth of the Tyne, in North- 

 umberland, southwards to Nottingham, and thence to the mouth 

 of the Teign in Devonshire. In the south-eastern counties 

 they underlie the tertiary rocks of the London and Hamp- 

 shire basins, as they are called, at no great depth from the 

 surface. Outlying patches of secondary rocks occur in Scotland, 

 where they are found near Brora on the east coast, and in the 

 islands of Skye and Mull on the west. In Ireland they are scantily 

 represented round about the neigh- 

 bourhood of Antrim. The second- 

 ary rocks are divided into 



I. Cretaceous. 



a. The Chalk is too well known 

 to need description, though techni- 

 cally it may be described as a soft 

 white limestone chiefly built up of 

 the microscopic shells of Foramini- 

 fera, and characterized in its upper 

 part by nodules and bands of flint. 

 These flints frequently inclose casts 

 of fossils (sponges, sea-urchins, etc.), 

 and sometimes shells themselves. 

 Fossils, too, are fairly abundant, scat- 

 tered throughout the mass. Amongst Ammonites various 

 the commonsr may be noticed the sea- (from the chalk), 



