406 TJpfield Green — The Cornish Beds and the Gedinnian. 



Onychia capuUforiiiis, Koch. ? Capulus Rhynchonella Uvonica, v. Bueli. 



subquadratus, Freeh. Rensallarin ? strigiceps, Roem. 



Pleurotomaria (?) striata, Goldf. /Spirifer primavus, Stein. 



Cmiocardittm, sp. Spirifer mercurii, Goss. 



Llmoptera (?) lepida, Saudb. Stropheodonta gigas, M'Coy. 



Lodanella mira, Kays. Athyris undata, Det'. 



Orthis circularis, Sow. TcntacuUtes grandis, Roem. 



Orthis personata {hipparionyx), Zeill. Nereitopsis eonmbieus, Green. 



Strophomena murchismii, A. & V. Petmia. 



Strophomena explanata. Pleiirodietyon prohlematicum, Goldf. 



We find the Dartmouth slates referred to by Williams ' as ' ichthyo- 

 ferous killas ' running along the coast to Old Mills, near Hendrasick, 

 with cleavage planes dipping south. A fault there would seem to 

 carry the strike of the beds north-west, and on the western side of 

 the fault they are tilted at a very high angle. 80-85° north-west, 

 the inclination gradually diminishing to 60-75° towards Talland 

 (where the variegation is well seen) and Polperro, continuing on 

 to a little west of Lantivet Bay (where the remains of Pteraspidian 

 fishes are unusually abundant). From this point they are deflected, 

 but have the same dip, leaving the Taunusian beds of Fowey to the 

 south, and continue on in a north-west direction through Ty wardreath 

 and St. Austell to St. Stephens, as described by De la Beche.- 



Until now we have only encountered the upper beds of the series, 

 but at St. Austell Bay a complicated system of faults alluded to by 

 De la Beche ^ has apparently caused an upcast of the country to the 

 west, and from this point the lower beds of the series, and at some 

 places even the subjacent older rocks, are exposed. These lower 

 beds consist chiefly of grits varying much petrologically, but mostly 

 felspathic. This variation in a coast deposit, Avhich would naturally 

 vary according to the rocks from which it is derived, is not surprising. 

 Subsequent earth-movements, folding, and overthrust faults, well 

 described by Hill* in his sketch of the Porthscatho and Falmouth 

 beds, account in many places for the immediate contiguity and 

 alternation of grits and slates, while during deposition sea currents 

 must have had a great local influence. 



The ti'end of the main northern mass of these grits is well 

 described by A. K. Barnett,^ who records " the occurrence of several 

 beds of arenaceous rocks approaching a conglomerate distinct from 

 the red and variegated sandstones and argillaceous slates associated 

 with them." " The most western of these beds at Petervale 

 St. Agnes, dip south with same dip at Callestock, in Chiverton 

 Valley, Beds having same line of strike at Marhasan Voaz, Tre- 

 worgan, St. Erme, Trehane Vean, Trewadra, and Cuskain, also in 

 the railway cuttings from Venton Glidor to Tarnoweth Wood, in 

 the road cutting between Grampound and Probus, and east from 

 Grampound to Pentuan Clifis. These beds have the same general 



1 Trans. Roy. Gaol. Soc. Cornwall, vi (1841), p. 124. 



- Report on Cornwall, pp. 80, 82. 



3 Report on Cornwall, p. 303. 



« Trans. Roy. Geol. Soc. Cornwall, xii (6), 1903, . 406. 



' Proc. Miners' Assoc. Devon and Cornwall, 1873, p. 93. 



