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



strongly characterized as green, blue, purple and gray (the 

 purple chiefly prevailing), in almost endless alternation, down 

 to the upper beds of No. 1: abundant facilities of identifying 

 and observing their striking peculiarities as contrasted with 

 all or either of the others, are afforded more especially by 

 the cliffs on either side the Tamar, from Plymouth up to 

 near Pentilly castle on the eastward region, and the shores 

 of the Padstow estuary on the west, from Wadebridge to 

 Stepper and Pentire points at its mouth. The sections and 

 succession of the same mineral beds, with the same fossils in 

 the upper ones, and the same apparent absence of them in the 

 lower, are so complete along the Padstow shores, that, re- 

 garding the same variegated beds underlying the same gray 

 calcareous slates, and these in their turn in like manner un- 

 derlying the arenaceous and coarse schistose deposits of No. 3 

 on the south, — all the facts and circumstances were too stri- 

 kingly associated in the same order to permit me to entertain 

 much doubt of their identity even at an early period of my 

 survey, before I had proved their continuity throughout the 

 intermediate region, and collected along the north shore of 

 the Padstow river a greater abundance of the same Trilobites, 

 Mollusks, Corals and Crinoidea, than I had gathered among 

 the same gray calcareous slates in the same relative position 

 near Plymouth. 



Another marked and peculiar feature of this series, com- 

 pared to Nos. 3 and 4, is the total absence of the red and gray 

 detrital aggregates, or their coarse arenaceous admixture, such 

 as obtained throughout No. 3; while among all its vast terms 

 below the level of the Plymouth limestones and their repre- 

 sentative gray calcareous slates, east and west, I have hitherto 

 been as unsuccessful as Professor Phillips and Mr. William 

 Sanders in discovering any organic remains. 



The limestones of Rock ferry opposite Padstow, — of But- 

 terville and Millaton near St. Germans, — of Plymouth, Yealm- 

 ton, Ugborough, Dartington, Berry- Pomeroy, Marldon, 

 Broadhempston, Ipplepen, Denbury, Abbot's and King's 

 Kerswell, Newton Bushel, and the east and west Ogwells, 

 belong to the upper terms of this series : judging from their 

 position and apparent underlie, and the intimate association 

 and intermixture of the purple and variegated slates, the Ip- 

 plepen, Denbury, Ogwells, and Newton Bushel limestones oc- 

 cupy a somewhat lower level than those of Little Hempston, 

 Bunkers hill (near Totness), Berry- Pomeroy, and Abbot's 

 and King's Kerswell, the latter being parted by, and associated 

 with, the upper gray calcareous and fossiliferous slates which 

 so commonly constitute the true equivalents of the Plymouth 



