TRIAS. 221 



TRIAS. 



The term Trias, introduced by H. G. Bronn, has been applied to 

 this series of rocks, on account of the triple division which they 

 exhibit in places on the Continent, where the three divisions are 

 (in descending order) Keuper, Muschelkalk, and Bunter. The 

 IVIuschelkalk, which (as its name implies) is a shelly limestone, has 

 not been identified in this country (see p. 208) ; we may, however, 

 include the Rhaetic Beds, and thus arrange our Triassic series as 

 follows : — 



p ', I Limestone, Shale, and Grey marl. 



Keuper | Red and variegated marl, and Dolomitic conglomerate. 

 Trias. -> Beds. ( Sandstone and marl. 



■R 1 Upper Mottled sandstone. 



•p ) I Pebble-beds. 

 ^ ■ ( Lower Mottled sandstone. 



In some localities there appear to be evidences of erosion or 

 disturbance between the beds classed as Bunter and those known 

 as Keuper, but there does not appear to be any satisfactory reason 

 to conclude that such unconformity was produced at one time over 

 the entire British area. Evidences of local erosion, as might be 

 expected, are not uncommon at various horizons in the Trias ; and 

 the apparent discordance between the Bunter and Keuper is in 

 some cases due to current-bedding. The beds indeed are subject 

 to so much change that different divisions, based on lithological 

 characters, may be made in different areas. The absence of the 

 Muschelkalk from the British area must not therefore be taken as 

 any evidence whatever of an unconformity, considering the very 

 variable nature of the Triassic strata, and of the conditions under 

 which the beds were deposited in different areas. ^ Calcareous 

 beds, at one time thought to represent the Muschelkalk, were, 

 however, noticed by Murchison at Broughton in Shropshire, and 

 similar beds have been observed in other localities in the West of 

 England.- (See sequel.) 



The use of the terms Bunter and Keuper is, however, convenient, 

 even if the beds in our country cannot be exactly correlated in 

 time with the rocks distinguished by those names on the Continent. 



The most remarkable fossils of the Trias are the Reptiles. 

 Among these are genera of Cj-ocodilia, Dinosaitria, and Lacertilia. 

 Of the Dinosauria, Pakwsaurus is noteworthy, as the Triassic 

 series has been named the Palasosaurian epoch by John Phillips.^ 

 Amphibia occur also, the footprints of the Lahvrmthodon being 

 not uncommon in some localities. Remains of Fishes, Entomo- 

 straca, and Plants have also been recorded. 



^ See De la Beche, Geol. Manual, p. 393 ; and Buckland, Proc. G. S. ii. 453. 



^ Silurian System, p. 37. 



^ T. H. Huxley, Q. J. xxvi. 42. 



