336 



TMASSIC GROUP IN ENGLAND. 



[Ch. xxn. 



Aust, in Gloucestershire, on the banks of the Severn, a dark-colored 

 stratum, well known by the name of the " bone-bed." It abounds in the 

 remains of saurians and fish, and was formerly classed as the lowest bed 

 of the Lias ; but Sir P. Egerton has shown that it should be referred to 

 the Upper New Red Sandstone, for it contains an assemblage of fossil fish 

 which are either peculiar to this stratum or belong to species well known 

 in the Muschelkalk of Germany. These fish belong to the genera Acro- 

 dus, Hybodus, Gyrolepis, and Saurichthys. 



Among those common to the English bone-bed and the Muschelkalk 

 of Germany are Hybodus plicatilis (fig. 432), Saurichthys apicalis 

 (fig. 433), Gyrolepis tenuistriatus (fig. 434), and G. Albertii. Eemains 

 of saurians have also been found in the bone-bed, and plates of an 

 Encrinus. 



Fig. 433. 



Fig. 434 



Fig. 432. 



Hybodus plicatilis. Teeth. Bone-bed. 

 Aust and Axmouth. 



Saurichthys apicalis. 

 Tooth : nat size, and 

 magnified. Axmouth. 



Gyrolepis tenuistriatus. 

 Scale; nat. size, and 

 magnified. Axmouth. 



The strata of red and green marl, which follow the bone-bed in the 

 descending order at Axmouth and Aust, are destitute of organic remains ; 

 as is the case, for the most part, in the corresponding beds in almost 

 every part of England. But fossils have been found at a few localities in 

 sandstones of this formation, in Worcestershire and Warwickshire, and 

 among them the bivalve shell called JPosidonia minuta, Goldf., before 

 mentioned (fig. 426, p. 334). 



The upper member of the English " New Red" containing this shell, 

 in those parts of England, is, according to Messrs. Murchison and 

 Strickland, 600 feet thick, and consists chiefly of red marl or slate, with 

 a band of sandstone. Ichthyodorulites, or spines of Hybodus, teeth of 

 fishes, and footprints of reptiles were observed by the same geologists 

 in these strata ;* and the remains of a saurian, called Rhynchosaurus, 

 have been found in this portion of the Trias at Grinsell, near Shrews- 

 bury. 



In Cheshire and Lancashire the gypseous and saliferous red shales 

 and clays of the Trias are between 1000 and 1500 feet thick. In some 

 places lenticular masses of rock-salt are interpolated between the argilla- 

 ceous beds, the origin of which will be spoken of in the sequel. 



The lower division or English representative of the " Bunter" attains 



* Geo!. Trans., Sec. Ser., vol. v. p. 318, <fcc. 



