30 THE GEOLOGICAL AGE OF CENTRAL AND WEST CORNWALL. 



whatever — indeed the character of the rocks woukl render their 

 occiirrence a matter of extreme improbability, except, of course, 

 in the included blocks. 



The grey quartzites of the parishes of Grorran and Veryan 

 have often been referred to by local writers, and they were long 

 ago found to be fossiliferous — and the fossils are undoubtedly 

 Lower Silurian ; a year or two since similar fossils were found 

 in the quartzites of the Meneage peninsula, south of the Helford 

 River, as described in my recent paper presented to the Royal 

 Geological Society of Cornwall."^' The fossils found are chiefly 

 brachiopods of the genus orthis — together with one or two 

 trilobites and an orthoceras. 



Mr. 0. W. Peach, in the year 1 844, gave a list of species then 

 in his possession, which included no fewer than nine species of 

 Orthis, two of Atrypa, and. one Leptcena.f These specimens 

 however — which are now in the Museum of the Royal Geological 

 Society of Cornwall — together with a large number of specimens 

 from other collections, have been recently examined with very 

 great care by Mr. Davidson, our greatest authority on the 

 brachiopoda, and he states, in a private communication with which 

 he has lately favoured me, that he is only able to make out 5 species 

 of orthis and one strophomena. He finds neither Leptcena novAtrypa. 

 If we add to these 6 brachiopods, one doubtful echinoderm 

 (sphaeronitus tesselatus according to Peach, loc. cit.)\ one, or 

 two species of Orthoceras (un-named as yet) and perhaps two 

 trilobites (one supposed to be Calymene Sternhergii by Peach, 

 and the other perhaps an Homalonotus) ; we have mentioned all 

 the fossils hitherto known as occurring in the quartzite. On the 

 whole it will, I dare say, be admitted that the quartzites may be 

 on the same geological horizon as the Caradoc Sandstone of the 

 typical Lower Silurian area — and as they occur near the top of 

 our 4 or 5 miles of Cornish Lower Silurians, we have ample 

 material beneath to supply all stratigraphical needs. 



The limestones usually occur in very thin and irregular beds of 

 no great extension either in strike or dip ? They contain 

 numerous fragments of encrinites, and of one or more species 

 of orthoceras 



* On the Geological Structure of the northern part of the Meneage 

 peninsula. Trans. Boy. Geol. 8oc. Corn. X, p. 47. 

 f Trans. Roy. Geol. Boc. Corn. VI, 1846. 



