ETHEKIDGE DEVONIAN ROCKS AND FOSSILS. 637 



the Middle or Upper Devonian, or the Carboniferous, and are there- 

 fore peculiar to the lower series of Xorth Devon. But Alveolites 

 suhorhicidaris, Orthis granidosa, 0. arcucita, and Spirifera Icevicosfa 

 occur in the Middle Devonian beds of South Devon, and S. hystericu 

 and Pterinea spinosa in rocks of the same age in Cornwall. 



The full relations of species occurring in the Lynton group of ^"est 

 Somerset and Xorth Devon cannot be clearly arrived at — so little, as 

 yet, being known of the fossils of the lower gritty slates of the 

 Quantock Hills, and of the lower beds that sweep round the Croydon 

 Hill promontory, north of Luxborough and Treborough Wood &c., 

 and also from the dif&culty we still have in assigning the true posi- 

 tion of the Cannington-Park limestone, though I have no doubt that 

 it belongs to the lowest part of the Middle Devonian Eocks. The 

 physical characters of this limestone more strongly resemble those 

 of the Torquay and Plymouth limestones than any in the Eorthern 

 area ; and the corals which occur in them are of the same species 

 as those of the middle series in the Quantook Hills ; but the crystal- 

 line structure of the rock seems to have obliterated nearlv all traces 

 of life. 



If we compare the species that are known to be peculiar to the 

 Lower or Lynton group of Xorth Devon, with those of the lower in 

 South Devon, as at Looe &c., and of that of Cornwall, only 1 species 

 is found to occur as common, viz. Leptcena laticosta ; whereas if we 

 examine and compare those species which are found in the three 

 areas occupied by the same rocks, a similar result takes place ; for 

 only two, and those corals, are known to occur in common to the 

 three areas, viz. Petraia Celtica and P. pJuriadialis, whatever this 

 may be. This is doubtless due to our incomplete knowledge of the 

 fauna of the three areas, and a proof how little we yet know of the 

 distribution of life through these obscure rocks ; they are facts, never- 

 theless, as based upon what is known. Be it remembered we have 

 here only examined and compared the Lower Devonian species 

 amongst themselves, not the relation of the Lower to the Middle or 

 Upper, where very different results will be found, tending to connect 

 them as one and a complete series in a very conclusive manner. 

 Careful search, then, gives us but 18 known species in the Lower 

 Devonian group of Pocks in Xorth Devon ; and 13 of these are found 

 and will be noticed as occurring in the Middle Devonian of either 

 North or South Devon. 



Table III. is constinicted to show the relation of the Lower 

 Devonian species of Britain to those of Europe, irrespectively of the 

 species passing into higher members of the Devonian series in any 

 area. It is singular that in the British Lower Devonian series there 

 is only 1 Gasteropod known in any area (viz. Pleurotomaria aspera), 

 only 4 LameUibranchs {Pterinea spinosa, P. anisota, Ctenodonta 

 Krachtce, and CUdopjhorus ovatiis), one Ce])h.alo])od(Orthocerasgracde), 

 and a solitary Nucleobranch {BeUerophon hisidcatus) ; and these are 

 from the lower series in Cornwall, the species found being either 

 deep-sea or pelagic forms, thus agreeing with the nature of the 

 deposits which contain them. 



