. Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments. Geology. 394 FOSSILS OF THE PORTLAND STONE. [Ch. XX. Fig. denuding waves or currents of the sea, or by a river; and many Pur- beck dirt-beds were probably formed in succession and annihilated, besides those few which now remain. The plants of the Purbeek beds, so far as our knowledge extends at present, consists chiefly of Ferns, Coniferae (fig. 380), and Cycadege (fig. 376), without any angiosperms; the whole more allied to the Oolitic than to the Cretaceous vegetation
. Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments. Geology. 394 FOSSILS OF THE PORTLAND STONE. [Ch. XX. Fig. denuding waves or currents of the sea, or by a river; and many Pur- beck dirt-beds were probably formed in succession and annihilated, besides those few which now remain. The plants of the Purbeek beds, so far as our knowledge extends at present, consists chiefly of Ferns, Coniferae (fig. 380), and Cycadege (fig. 376), without any angiosperms; the whole more allied to the Oolitic than to the Cretaceous vegetation. The vertebrate and invertebrate animals indicate, like the plants, a somewhat nearer relationship to the Oolitic than to the Cretaceous period. Mr. Gone of a pine from the Brodie has found the remains of beetles and sev- isieofPurbeck. (Fitton.) Qm\ insects of the homopterous and trichopterous orders, some of which now live on plants, while others are of such forms as hover over the surface of our present rivers. Portland Oolite and Sand (5, Tab., p. 375).—The Portland oolite has already been mentioned as forming in Dorsetshire the founda- tion on which the freshwater limestone of the Lower Purbeck reposes (see p. 389). It supplies the well-known building-stone of which St. Paul's and so many of the principal edifices of London are construct- ed. This upper member rests on a dense bed of sand, called the Portland sand, containing for the most part similar marine fossils, below which is the Kimmeridge clay. In England these Upper Oolite formations are almost wholly confined to the southern coun- ties. Corals are rare in them, although one species is found plenti- fully at Tisbury, "Wiltshire, in the Portland sand, converted into flint and chert, the original calcareous matter being replaced by silex (fig. 381). Fig. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance
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