§ 7. ORGANIC REMAINS OF THE TRIAS. 545 



Lydian- stone, granite, jasper, porphyry, slate, &c. seem to 

 have originated from rocks formerly connected with the 

 range of Charnwood Forest. Still nearer the Charnwood 

 hills, the finest sandstone contains fragments of slate. Mr. 

 Bakewell was of opinion that a large proportion of the ma- 

 terials of the Triassic strata was derived from trap and other 

 igneous rocks; and that the red marl was the debris arising 

 from the decomposition of the less indurated volcanic pro- 

 ducts ; hence, probably, the extreme fertility of the soil.* 



But the most interesting of these conglomerates, or 

 breccias, in England, are those in which eruptions of lava 

 appear to have been thrown into the ocean of the New Red, 

 and to have cemented together the water-worn materials, so 

 as to form a trap conglomerate ; such, at least, seems to have 

 been the origin of the amygdaloidal trap, as it is termed, in 

 the vicinity of Exeter. f A few miles to the south of that 

 city, masses of a rock of this kind are interposed between 

 beds of sandstone ; the general appearance of the stone is 

 that of a granular rock, somewhat loosely compacted, of a 

 purplish-brown colour, interspersed with minute portions of 

 calcareous spar, mica, and indurated clay tinged by copper 

 or manganese. It is full of small cells, which are either 

 filled or lined with manganese, calc-spar, or jasper ; a 

 structure termed in geology amygdaloidal, or almond-like : 

 the substance of the rock is an earthy felspar. 



7. Organic Remains of the Trias. — This formation 

 presents a remarkable contrast with that of the Jurassic, in 

 the paucity of organic remains ; for while the latter teems 

 with marine fossils, the former, throughout immense areas, 

 is almost wholly destitute of any vestiges of animals or 

 vegetables ; a proof that the strata were, for the most part, 

 accumulated under conditions unfavourable for the preser- 

 vation of organic structures. Several fucoid plants, and 



* Introduction to Geology, fifth edition, p. 279. 

 f Geology of England and Wales, p. 294. 



