The Devonian Rocks of South Devon. 195 



including the absence of stratification, the presence of splinters of 

 rock like that of the overlying limestone cliffs, the scarcity of rounded 

 pebbles, and the great abundance of sharply fractured shells asso- 

 ciated with unbroken rock- dwelling shells. 



He enumerated the fossils collected from these deposits by Mr. A. 

 R. Hunt, which include Trophon truncatus and Fleurotoma turricala, 

 and calling attention to the observations of Messrs. Feilden and 

 De Ranee, and of Dr. Moss upon the ice-foot of Arctic regions, 

 and the accumulation of material in the trenches found therein 

 concluded that the deposits under consideration were formed at 

 a time when a small bay existed between Hope's Nose and the 

 Thatcher Rock, which has since been destroyed by denudation of the 

 intervening sandstone, in which bay an ice-foot once existed ; and 

 further, that the two deposits form the surviving relics of the mingled 

 mass of chips, shells, shell-fragments, Crustacea, &c, which must 

 have filled the trench in the ice-foot demanded in such a position. 

 This would place the time of formation of the deposits at the close 

 of the Glacial period. 



2. " The Devonian Rocks of South Devon." By W. A. E. Ussher, 

 Esq., E.G.S., of H.M. Geological Survey. 



This paper is the result of work done in continuation of the labours 

 of the late Mr. Champernowne, and refers particularly to the area 

 north of the Dart and east of Dartmoor. 



Owing to the complicated stratigraphy of the region, we have to 

 fall back upon such information as can be procured of the general 

 types of Upper, Middle, and Lower Devonian faunas ; for though the 

 lithological constituents of these three divisions are broadly distin- 

 guishable, there are no definite lithological boundaries between them. 



The Lower Devonian is mainly distinguished by the occurrence 

 of sandstone and grit, but the upper beds are shales passing into 

 the Middle Devonian slates. 



The Middle Devonian consists of limestones, and shaly limestones 

 upon slates, the latter representing the Calceolen-Schiefer, and con- 

 taining Sjnnifer speciosus. String ocephedus is found here and there 

 in the middle Devonian Limestones. The upper part of the middle 

 Devonian Limestones (with Lummaton fauna) passes into the 

 cuboides-be&s of the Upper Devonian. The Upper Devonian con- 

 tains thin-bedded limestones, often concretionary, with chocolate- 

 red and pale greenish slates and mudstones. These beds corre- 

 pond to the Goniatiten-Schichten, Kramenzelstein and Knollenkalk 

 of Germany, and to the Cypridinen-Schiefer. 



In the Upper and Middle Devonian rocks we find a local preva- 

 lence of schalstein and tuffs, breaking up the limestones. The slate 

 and sandstone type of Upper Devonian in North Devon appears to 

 give place southward to a purely slate type, possibly accompanied by 

 overlap of the Culm measures. The author groups the South Devon 

 rocks under the following heads : — 



