338 The Rev. D. Williams on the Killas Group of 



elbow with a flexured outline, from the inner angle of which 

 No. 4 killas is deflected with them into a nearly north and 

 south strike after the Fowey river and its eastward and west- 

 ward banks. 



With the exception of fish, other organic remains appear 

 to be very rare; Mr. Couch, jun., however, has discovered 

 several specimens of a small or young Bellerophon at Polperro, 

 and I have collected Spirifers, &c. up the Dart, and Corals and 

 Crinoidea in it at Whitsand bay, and Beeson and Hall sands 

 near the Start. 



An abandoned mine near Lansallos, apparently one of the 

 many monuments in Cornwall of the speculative epidemic of 

 1835, is the only instance I remember of any workings for 

 metals, either ancient or modern, throughout its entire range. 

 It affords good blueish-gray roofing-slates near Dartmouth, 

 and would yield them also at other localities, probably, if 

 sought for, but I know of no other quarries. 



I have gone into details in regard to this series more pre- 

 cisely and particularly than I propose to give of the others, 

 because its true position, and its relations to them, have hitherto 

 been altogether mistaken : that it does not underlie the great 

 killas mass, or in any way constitute " a south Devon axis," 

 nor in any sense correspond with either of the Exmoor series, 

 must be obvious from these structural details, and the fact 

 that it is of posterior formation to the floriferous and carbona- 

 ceous rocks. The distance in miles, in fact, along which it 

 gives steady southward dips compared to that at which its 

 beds are reversed and present northern dips (to say nothing 

 of the permanent underlie of the abundantly fossiliferous and 

 metalliferous killas No. 3, the next in descending order), is 

 thirty-four of the former and eighteen of the latter. 



No. 3, or the metalliferous killas, is in almost diametrical 

 mineral and organic contrast to the former series, so much so 

 that anything like glossy, delicate and crystalline slate, and 

 fish remains, are as rare exceptions in it as metalliferous lodes 

 and red and gray sandstones, and coarse arenaceous schists, 

 with innumerable organic remains of many genera and spe- 

 cies, are in the other. The abundant evidences of its under- 

 lying the fish-bearing killas No. 4, have been referred to in 

 the description of that series. 



No. 3 may be described as a vast detrital deposit of red 

 and gray grits, containing throughout greater or less admix, 

 tures of volcanic ash or mud, in the form of blue or gray 

 schists, red slates, &c. From this circumstance, and the 

 enormity of its mass, it constitutes a broad and well-defined 

 line of demarcation, and an invaluable middle term in a classi- 



