LARK: ON THE TRIASSIC BOULDER, &c 
71 
the Atrypa, Strophomena depressa, Spirifers, Rhynconella 
Wilsoni, Murchisonia gracilis, Trochus, and Trilobites 
(Phacops candatus and Encrinurus punctata). 
Although, as will have been seen from the description, 
there may seem some room for doubt as to the true horizon 
of these pebble beds, yet the evidence, especially in the 
cuttings where the pebbles were interbedded among soft 
sandstones, seemed to point pretty conclusively to their 
Triassic origin. This conclusion rests further upon the 
unusual solidity of the beds — some of the sands exactly re- 
sembling the Bunter sections first mentioned — the remark- 
able series of faults, and the " burnt " condition of the quartz 
pebbles, wherever those occurred. 
The beds, however, represented in Fig. 3, which occur 
just before we come upon the Wenlock shales at Aldridge, 
may very well be of Permian age. Their character was 
different from the previous, containing more clay and less 
pebbles, and the dip greater. According to Ramsay's map, 
the Permian is overlapped by the Bunter a very little to the 
south, perhaps as much as half a mile ; but the frequent 
difficulty of fixing the exact position of the boundary 
between these two formations is well known. 
There yet remains the very interesting question as to 
the origin of these beds, with which is involved the still 
more debatable point — Do such deposits bear witness to 
ancient periods of glacial action \ About this there appears 
to be the greatest diversity of opinion, and I do not pretend 
to make an assertion where so many able investigators 
remain undecided. But we may profitably compare them 
with other similar deposits. In the same district are the red 
gravels around Birmingham, already noticed, and usually 
considered to be connected with the Glacial Epoch. The 
Norfolk deposits afford several very similar sections, which 
I examined with much interest in 1876, along the new line 
from Cromer to North Walsham, between Gunton and the 
