4 SUPPLEMENT TO THE 



As the great divisions of systems introduced by geologists into the regular sequence 

 of formations have been proposed more for convenience of reference than as indicating the 

 existence of completely independent periods, vi^e should accept these divisions or systems 

 in a general sense. The more we advance in our knovy^ledge we find that in nature such 

 sharp lines do not exist, and that passage-beds will turn up between two consecutive 

 systems supposed to be entirely distinct. This indisputable fact has been very often 

 demonstrated, and in particular in the case of the Upper-Devonian and Lower- 

 Carboniferous formations. It would, therefore, be incorrect to assert, as Jukes has 

 endeavoured to do, that the Devonian rocks are the equivalents of the Carboniferous 

 Slates of Ireland. Palseontologically the Silurian, Devonian, Carboniferous, and Permian 

 formations are, in the main, characterised by distinct faunas, although a certain number 

 of species do in reality pass from one contiguous formation into the other. As far as the 

 Brachiopoda are concerned, it may be asserted, in tbe state of our present information, 

 that but few species are common to the Silurian and Devonian, but that a larger 

 number have been found to be common to the Devonian, Carboniferous, and Permian. 



There are, however, some difficult geological questions still to be solved with respect 

 to the subdivisions of the Devonian formation, but which cannot be entered upon in 

 the present Supplement. 



I have little or nothing new to add with respect to the species that occur in the Upper 

 and Lower Devonian formations. These, as a rule, are not found in a very good state of 

 preservation, as they occur chiefly in the condition of casts or flattened impressions, often 

 much out of shape. 



At Saltern Railway Cutting (behind Saltern Cove, within four or five miles of Torquay) 

 Mr. J. G. Greenfell and Mr. G. F. Whidborne came upon a light brownish-red shale in 

 which several species of Brachiopoda occurred in considerable numbers, accompanied by 

 Pleurodictyum froblematicum and Petraia, sp. The fossils occur in the condition of 



Woolborough quarry is adjacent to the road from Newton Abbot to Totnes, in South Devon, a short 

 mile from the former. 



The limestone quarries grouped under the general name of Ogwell are in the immediate neigh- 

 bourhood of Chircombe Bridge on the River Lemon, about two miles west of Newton Abbot. Looe 

 Harbour in Cornwall is from thirteen to fourteen miles almost due west from Plymouth. 



Mr. N. H. Valpy, in his ' Notes on the Geology of Ilfracombe and its Neighbourhood,' 2iid edition, 

 gives a list of the Brachiopoda which he finds in the Ilfracombe series, from the Trentishoe and Hangman 

 Grits to the Morte Shales inclusive, viz. : 



Athyris concentrica. 



— lacryma ? 

 Atrypa desquamata. 



— reticularis. 



— aspera. 

 Cyrtina heteroclita. 

 Merista plebeia. 

 Orthis interstrialis ? 



Orthis striatula. 

 Rensselceria stringiceps. 

 Rhynchonella cuboides, 



— pugnus. 



— ])leurodon. 

 Spirifera curvata. 



— Verneuilii, 



— nuda. 



Spirifera speciosa. 

 — cristata ? 

 Stringocephalus Burtini. 

 Strophomena crenistria. 



— mnbraculum. 



— rhomhoidalis. 



