Oh. XXII.] 



TRIASSIC GROUP IN ENGLAND. 



441 



Different members of the above group rest in England, in some 

 region or other, on almost every principal member of the palaeozoic 

 series, on Cambrian, Silurian, Devonian, Carboniferous, and Permian 

 rocks, and there is evidence everywhere of disturbance, contortion, 

 partial upheaval into land, and vast denudations which the older 

 rocks underwent before and during the deposition of the successive 

 strata of the New Red Sandstone group. It was stated (p. 419) that 

 the Lower Lias in the southwest of England contained near its base 

 strata characterized by Ammonites planorbis, below which beds with 

 many reptilian remains sometimes occur. 



Still lower, on the boundary line between the Lias and Trias, cer- 

 tain cream-colored limestones, called "White Lias by Smith, are found 

 usually, but not always, without fossils. These white beds have late- 

 ly been reTerred by Mr. Chas. Moore to what he calls the Rhastic beds,* 

 because largely developed in the Khsetian Alps, and which are the 

 same as the Koessen beds of Germany, No. 1, p. 435. The marine 

 organic remains observed in them near Frome, in Somersetshire, show 

 that they appertain to the highest member of the Upper Trias, in 

 which occur the sandstones and shales with Avicida contorta (fig. 479), 

 together with other fossil shells belonging to the same zone in Ger- 

 many, France, and Lombardy. Among the most abundant of the 

 shells in all these countries is the above-mentioned Avicula (fig. 479), 

 and with it Cardium rhceticum (fig. 477) and Pecten Valoniensis 

 (fig. 478). 



Fig. 478. 



Fig. 477. 



Fig.* 4 



Cardium rhceticum. 



£Jat. size. Uppermost 



Trias. 



Pecten Valo?iiensis, Dfr. 

 £ nat. size. Portrush, 

 Ireland, &c. Uppermost 

 Trias. 



Avicula contorta. Portlock. 

 Portrush, Ireland, &c. 

 Nat. size. Uppermost 

 Trias. 



The principal member of this group has been called by Dr. Wright 

 the Avicula contorta bed,f as this shell is very abundant, and has a 

 wide range in Europe. General Portlock first described the forma- 

 tion as it occurs at Portrush, in Antrim, where the Avicula contorta 

 is accompanied by Pecten Valoniensis, as in Germany. The beds 

 under consideration, although of moderate thickness, are already rich 

 in synonyms, as, besides the German names mentioned at page 435 



* Moore, Rhsetic Beds, Quart. Geol. Journ., 1861, vol. xvii. 



| Dr. Wright, on Lias and Bone-bed, Quart. Geol. Journ., 1860, vol. xvi. 



