166 W. A. E. Ussher — Subdivisions of the Trias. 



sequently it is much affected by faults, which obscure the relations 

 of the varieties composing it to each other, and to which, in almost 

 every instance, in the district under consideration, its local absence 

 is clue. The feature made by the Pebble beds, noticed by Mr. 

 Pengelly, maintains over the whole area, marking the line of faults 

 where the division is unrepresented at the surface. Between "Whimple 

 and Ottery St. Mary the large quartzite pebbles give place to smaller 

 ones of quartz and grit ; the beds, as at Uffcidm, are sometimes 

 compacted, sometimes gravelly, as at Burlescombe. At White Ball 

 Hill tunnel the Pebble beds give place to Conglomerates, containing 

 large limestone pebbles, besides those of grit and quartz. The beds 

 are generally massive. Both Pebble beds and Conglomerates contain 

 impersistent beds of sand and sandstone, and in some instances are 

 partially replaced by them. 



4. — The Lower Marls. 

 The division underlying the Pebble beds and Conglomerates, 

 I have called Lower Marls, to distinguish it from the Upper 

 Marls, It consists of red marls, variegated greenish-grey, much 

 faulted in the lower beds on the coast of Devon, between 

 Exmouth and Budleigh Salterton, where it contains beds of 

 sandstone. North of Exeter its true nature is very generally con- 

 cealed by a thick loamy clay soil, and as the beds of sandstone are 

 not traceable, they may be absent, or indicate a passage to the under- 

 lying series, only in places where its upper variety consists of 

 sandstones. 



5. The Lower Sandstones and Breccias. 



This is the most variable member of the group, and as a desci'iption 

 of all its phases with which I am already acquainted would occupy 

 more space than is allotted to the whole of this brief notice, we will 

 only glance at a few of the salient points. 



At Exmouth, as the junction between this division and the Lower 

 Marls is a faulted one, I am forced to concede the entire absence of 

 sandstones, which are developed at Topstham, to that cause, so that 

 between the coast of Devon and Burlescombe the upper variety of 

 this division consists of sandstones; but, from Burlescombe to Williton 

 they seem to occur generally at the base of the series. Beds of sand 

 and sandstone, intercalated with the breccias, occur at any horizon 

 in the lowest division. They consist of red rock-sands and sand- 

 stones ; variegated near Torquay ; are sometimes stained blackish ; 

 seldom very calcareous, and only locally contain calcareous nodules. 



Similar varieties of Breccia occur at different horizons in the 

 division, in different places : For instance, the hard Breccias of 

 Teignmouth, and those of Heavitree and Sampford Peverell (east of 

 Tiverton), contain subangular, angular, and occasionally a few 

 pebble fragments of grit and quartz, with limestone in the first and 

 last instances, and igneous rocks in the first and second. The brec- 

 cias of Dawlish and Exmouth present the appearance of hard red 

 rock-sand, from which the stones, which are generally small, are 

 weathered in relief, by their superior hardness ; allied breccias occur 



