92 REPORT — 1860. 



is continued in ascending order to the slates on the north shore of Barnstaple Bay; 

 but its very highest beds are seen on the south shore of the bay, dipping under the 

 base of the culm- measures. 



"The equivalent of this third and highest Devonian group is found to the south of 

 the great culm-trough in a group, near the top of which appear the limestone bands 

 and fossiliferous slates of Pethenvin. It may be called the Barnstaple or Petherwin 

 group*." 



Professor Sedgwick recognizes the Plymouth group in the slates of Looe, Polperro, 

 and Fowey in Cornwall f. 



Accepting, at least provisionally, these divisions, we have, when considered chro- 

 nologically as well as geographically, what, as a matter of convenience, may be called 

 five fossiliferous areas; namely, a deposit of the age of the Plymouth group in each of 

 the districts, South Devon, North Devon, and Cornwall ; and one of the Barnstaple 

 age in each of the two latter. To avoid undesirable repetition, the)' will be spoken of 

 throughout this paper as Lower South Devon, Lower North Devon, Lower Cornwall, 

 Upper North Devon, and Upper Cornwall. The terms " Lower" and " Upper" are 

 to be understood as applied relatively only to the rocks of Devon and Cornwall, and 

 not as embodying or implying any opinion respecting the co-ordination of these rocks 

 with deposits of the Devonian age elsewhere. 



Had existing materials warranted it, it would have been desirable to have made a 

 farther division, namely, one having reference to the mineral character of the depo- 

 sits, as well as to time and place ; for it is certain, as might have been expected, that, 

 in the same area, some fossils are peculiar to the argillaceous beds, and others are 

 found only in the calcareous strata; thus, for example, I learn from Mr. Godwin- 

 Austen that he has found the remarkable coral Pleurodictyum problemalicum in the 

 slates, but not in the limestones, at Ogwell in South Devon. My own experience is 

 in harmony with this; the same fossil occurs in the slates at Torquay and, in great 

 abundance, at and near Looe in Cornwall ; but not in limestone anywhere. At pre- 

 sent, however, it would be premature to attempt a division of this kind. 



The object contemplated in the present paper is to give some account of the ancient 

 population of the five areas, especially with reference to their distribution, so far as it 

 was known when the Census was last taken. 



Amongst the things which have recently drawn my attention to this subject may be 

 mentioned the following passage in the address of Professor Phillips as President of 

 the Geological Society of London. " Only a small proportion of the fossils of North 

 Devon occur in South Devon J." And also the following statement by Professor 

 Haughton : — " I do not believe in the lapse of a long interval of time between the 

 Silurian and Carboniferous deposits, in fact in a Devonian period. 



" The same blending of corals has been found in Ireland, the Bas Boulonnais, and 

 in Devonshire, where Silurian and Carboniferous forms are ol common occurrence in 

 the same localities §." 



It should be remembered that the statement with which we have here to deal is that 

 the "blending of corah" (the word is not fossils) "of Silurian and Carboniferous 

 forms is of common occurrence in Devonshire.'' 



I have consulted such registers as I have been able to command, and have thrown 

 so much of their contents as bear on the questions before us into the following tabular 

 form, for which, of course, no higher value is claimed than attaches to the original 

 documents. 



The materials have been in a great degree derived from Professor Morris's ' Cata- 

 logue of Fossils.' 



Every geologist must, of course, be aware of the numerous and elaborate Tables 

 which Professor Phillips has introduced in his ' Palaeozoic Fossils of Devon and 

 Cornwall,' when discussing subjects akin to those at present under consideration. In 

 the preparation of this paper the author has in no way made use of the valuable data 

 these Tables contain. 



* Quarterly Journ. Geol. Soc. vol. viii. p. 3. t Ibid. p. 14. 



t Quarterly Journ. Geol. Soc. vol. xvi. p. xl. 



§ Voyage of the ' Fox ' in Arctic Seas, Appendix, No. IV. p. 387. 



