100 



REPORT — 1860. 



were forms referable to each of these faunas, yet this did not deter him from making 

 the suggestion, even in the face of a physical difficulty connected with the culmiferous 

 beds of North Devon — subsequently removed by Prof. Sedgwick and Sir It. I, Mur- 



clnson. 



1SUII. 



And what has been the efFect of the recent progress of discovery and nicer discri- 

 mination on this question? Has it increased or decreased the evidence in favour of 

 a Devonian period? In IS 16 Sir II. De la Beehe, discussing this subject, gave a 

 total of 190 species noticed in South Devon which he disposed of thus : 75 Carboni- 

 ferous forms, 10 Silurian, S common to Silurian and Carboniferous, and 07 peculiar 

 to Devonshire*. At present — confining ourselves also to South Devon — the lists give 

 a total of 226, of which 34 are Carboniferous, 6 Silurian, not one common to both, 

 and 186 peculiar to the district; or putting the totals at each period =1000, and 

 equating the separate numbers to this, the figures stand as ill the following Table, and 

 show a decided advance Devonianward. 



Table VI. 



Doubtless the fact that the Carboniferous forms so greatly outnumber the Silurian 

 has a meaning. Does not this greater organic affinity betoken a closer chronological 

 connexion with the more recent than the more ancient period ? Is it not an intima- 

 tion that the lowest beds of Devonshire do not constitute the basement of the Devo- 

 nian system? That the county has an ample development of Upper and Middle, but 

 not of Lower Devonian rocks?" 



Hitherto we have accepted the hypothesis that the South Devon rocks are more 

 ancient than the Barnstaple and Petherwin groups, and that the two last are contem- 

 poraries. It may perhaps be well before concluding this paper to glance at the bear- 

 ings of the palajontological evidence at present before us on this point. Putting the 

 entire series of fossils found in each of the three districts=1000 and equating accord- 

 ingly, the numbers stand as below. 



Table VII. 



Whence it seems tolerably safe to infer that neither of the three deposits is Carboni- 

 ferous or Silurian, but intermediate, having a closer connexion with the former than 

 the latter period, and that South Devon is the most ancient of the three groups; but 

 the evidence is scarcely strong enough to carry any conclusion respecting the relative 

 age of the remaining two; so far as it goes, it amounts to no more than a suggestion 

 that Petherwin is rather more modern than Barnstaple. Be that as it may, the fossils 

 found common to South Devon and each of them must be regarded as contributions 



* "Memoirs" of Geological Survey, vol. i. p. 96. 



