366 
ELEMENTS OE GEOLOGY. 
CHAPTER XXL 
TRIAS, OR NEW RED SANDSTONE GROUP. 
Beds of Passage between the Lias and Trias, Rhaetic Beds.—Triassic Mam- 
mifer.—Triple Division of the Trias.—Keuper, or Upper Trias of England. 
—Reptiles of the Upper Trias.—Eoot-prints in the Bunter formation in 
England.—Dolomitic Conglomerate of Bristol.—Origin of Red Sandstone 
and Rock-salt.—Precipitation of Salt from inland Lakes and Lagoons.— 
Trias of Germany.—Keuper.—St. Cassian and Hallstadt Beds.—Peculiar¬ 
ity of their Fauna.—Muschelkalk and its Fossils.—-Trias of the United 
States.—Fossil Foot-prints of Birds and Reptiles in the Valley of the Con¬ 
necticut.—Triassic Mammifer of North Carolina.—Triassic Coal-field of 
Richmond, Virginia.—Low Grade of early Mammals favorable to the The¬ 
ory of Progressive Development. 
Beds of Passage between the Lias and Trias—Rhastic Beds, 
—We have mentioned in the last chapter (p. 356) that the 
base of the Lower Lias is characterized, both in England and 
Germany, by beds containing distinct species of Ammonites, 
the lowest subdivision having been called the zone of Am- 
monites planorhis, . Below this zone, on the boundary line 
between the Lias and the strata of which we are about to 
treat, called “Trias,” certain cream-colored limestones de¬ 
void of fossils are usually found. These white beds were 
called by William Smith the White Lias, and they have been 
shown by Mr. Charles Moore to belong to a formation simi¬ 
lar to one in the Rhsetian Alps of Bavaria, to which Mr. 
Gtimbel has applied the name of Rhaetic. They have also 
long been known as the Koessen beds in Germany, and may 
be regarded as beds of passage between the Lias and Trias. 
They are named the Penarth beds by the Government sur¬ 
veyors of Great Britain, from Penarth, near Cardiff, in Gla¬ 
morganshire, where they sometimes attain a thickness of 
fifty feet. 
The principal member of this group has been called by Dr. 
Wright the Amciila contorta bed,^as this shell is very abun¬ 
dant, and has a wide range in Europe. General Portlock 
first described the formation as it occurs at Portrush, in An¬ 
trim, where the Avicula contorta is accompanied by Pecten 
Yaloniensis^ as in Germany. 
The best known member of the group, a thin band or bone- 
breccia, is conspicuous among the black shales in the neigh- 
* Dr. Wright, ou Lias and Bone Bed, Quart. Geol. Journ., 1860, vol. xvi. 
