682 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



should be expected. Out of tlie 17 species therein given, there are but 

 8 known in any part of the Carboniferous rocks in any area ; they are 

 the following : — Actinocrinus tenuistriatus, Cyathocrinus variabilis, 

 Athyris concentrica, Rhynchonella pleurodon, B. jpugnus, Spiriferina 

 cristata, JStrophomena rhomhoidalis, Streptorhynchus crenistria. 



The 17 enumerated species, taking them as they stand, are known 

 to most observers to occur in the N'orth Devon Devonian rocks ; but 

 we have yet to learn that the fossils or rock-masses occupying the 

 areas north and south of Pick well Down are on the same general 

 horizon, and are equally Carboniferous Slate ; until this be the case, 

 none of the 17 forms enumerated can be compared. Every name in 

 the column marked South, except perhaps Barnstaple, and every 

 species save the 8 given above, are recognized as Upper Devonian 

 localities and species. Assigning to them therefore a north and south 

 position and distribution geographically, by virtue of a so-called 

 " central band " of Old Eed Sandstone, whose position is neither 

 central nor dubious in North Devon, shows upon paper a comparison 

 that is not to be found in the physical structure of the country. 

 Admit that all North Devon is Carboniferous Slate, and then the 

 above 17 and all the other fossils are of that age ; until then, 9 of 

 them, viz. Petraia pleuriradialis, Fenestella antiqua, Pleurotomaria 

 aspera, Bellerophon glohatus, Athyris concentrica, OrtJiis interlineata, 

 0. striatula, Spirifera Icevicosta, and Phacops latifrons, will stand as 

 Devonian species ; and let me add that, of the whole 17 in the Table, 

 the doubtful Chonetes Hardrensis is the only one common to the 

 Lower or Lynton group and the Carboniferous Slate either of Devon 

 or Ireland. 



At p. 366 of same paper, it is stated that our choice is " now, 

 however, limited to the period of the Old Red Sandstone and that of 

 the Carboniferous Limestone, unless we assign to them [the fossils] 

 a hitherto undefined period between those two, or suppose tliem to 

 be older than those of the Old Red Sandstones " (the whole of that 

 formation according to Prof. Jukes's views, but which I would call 

 Upper Devonian, or Upper Old Red Sandstone ; therefore no one 

 would suppose that the Carboniferous preceded the Devonian). 



The fact that the Devonian fauna contained some species belong- 

 ing to genera peculiar to or only previously known in the older Silu- 

 rian rocks, such as Phacops, Homcdonotus, Bronteus, Cheirurus, and 

 Harpes among the Crustacea, the genus Spirifera and Pentamerus 

 among the Brachiopoda, &c., but species of which do not occur in the 

 Devonian or Carboniferous, tends to clearly establish passage and 

 connexion at some unknown locality ; and our one connecting 

 species, Atrypa reticularis (numerically so great), which was so 

 common in the whole of the Upper Silurian seas, would tend to show 

 strong grounds for determining the Lower Devonian to be contem- 

 poraneous with the Lower Old Red Sandstone of the Silurian region, 

 which is there conformable to the Silurian rocks, but totally distinct 

 in life-remains a few feet above the passage-beds. 



I have shown what species occur in common between the Devo- 

 nian and Silurian, and what are common to the Lower Old Red, 



