1863.] 



SALTER UPPER OLD RED SANDSTONE. 



483 



result of a short visit to the southern side of the culm- trough, in the 

 autumn of 1857. The Torquay section was briefly examined, and 

 its correspondence with that of the Spirifer-sandstone group of the 

 Rhine, as given in ' Siluria,' easily perceived. 



The fossils of the ordinary Plymouth limestones, of all colours, are 

 so well known that no time need be spent in proving them to be the 

 equivalents of the Eifel limestone, or of the Combe Martin limestones 

 of North Devon. Unfortunately the special object on which I was 

 sent did not permit me to examine the Newton Bushel section*; 

 but or crossing the Devonian slates from Plymouth, by Tavistock, 

 to Launceston, I found everywhere the same silvery slate which 

 must be familiar to every geologist who has visited Ilfr^combe. Nor 

 was I then aware of the importance of identifying the red band of 

 the Morte slates with the beds about Launceston and Petherwin, 

 though I now believe them to be equivalents — a point of no little 

 importance in the geology of Devon and Cornwall ; for, in a tole- 

 rably careful survey of the Launceston beds, I fully convinced myself 

 (and, on my return, Sir Roderick Murchison) that the Petherwin 

 limestone-group did not represent the Barnstaple series, as had been 

 formerly supposed, but that it was a lower band in the Devonian 

 series f . The reason for this determination will appear by comparing 

 the following list of fossils, all of which came from the Landlake 

 and Petherwin quarries, with those above named from the " Mar- 

 wood group." 



List of the Petherwin and Landlake Fossils ( Upper Devonian). 



Pterinea ventricosa. 

 Avicula subradiata. 



exarata. 



Cardiola retrostriata (Cardium pal- 



matum). 

 Strophalosia caperata, rare. 



membranacea, more frequent. 



subaculeata (Leptama laxispina, 



L. fragaria, &c), abundant. 

 Orthis interlineata. 



resupinata. 



Streptorhynchus crenistria. 

 Spirifer protensus. 



Petraia Celtica. 

 Aniplexus tortuosus. 

 Cyathophyllum caespitosum. 

 Fenestella laxa. 



antiqua. 



Sanguinolaria ? sulcata. 

 Ctenodonta (Pullastra) elliptica. 

 Orthonota (Cypricardia) semisulcata. 

 Axinus (Cypricardia) deltoideus. 

 Aviculopecten granulosus. 



transversus. 



alternatus. 



arachnoideus. 



* I have lately seen it, for a single day, in company with Mr. W. Vicary, of 

 Exeter. It is clear enough that there is an Upper as well as a Middle Devonian 

 series in this place, the lower limestones of Bradley Woods being quite different 

 from the higher, close to the town, and containing different fossils. The Upper 

 or Clymenia-limestones must have existed close by, as pebbles from them, con- 

 taining the ClymenicB, are abundant at Teignmouth (Shaldon). 



f That this determination is not without its value will ajDpear on comparing 

 the statements made to the above effect in ' Siluria,' p. 300, with those in the 

 Preface to the 2nd Fasciculus of Prof. Sedgwick's Cambridge work, 1852, or 

 more lately in the excellent Synoptical Table by Professor King, of Gralway, in 

 which these authors place the Petherwin Slates with Clymenia (the true Upper 

 Devonian of the Continent) above the Marwood or Coomhola group. In the 

 Continental sections one or other of these is frequently absent, the true reason 

 for which will be apparent as we proceed. 



