TUE GEOLOGIST. 



five CarbouiftTOUs forms, ten Silurian, eight common to-Silurian and 

 Carboniferous, and ninety-seven — slightly more than half — peculiar 

 to Devonshire.* At present (continiug ourselves also to South 

 Devon) the catalogue gives a total of two hundred and twenty-six, 

 of which thirty-four are Carboniferous, six Silurian, and a hundred 

 and eighty-six peculiar to the district ; or putting the totals at 

 each period = 1000, and equating the other numbers to this, the 

 figures stand as in the following table, and show a decided advance 

 Devonian- ward. 



TABLE VIII. 





1846. 



1860. 





53 



26-5 





395 



150-5 



Siliu-ian and CarLouiferous 



42 



00 





510 



828-0 





1000 



1000 



Doubtless the fact that the Carboniferous forms so greatly out- 

 number the Silurian has a meaning. Does not this greater organic 

 afiinity betoken a closer connection with the more modern than with 

 the more ancient period ? Is it not an intimation that the lowest 

 beds of Devonshire do not constitute the basement of the Devonian 

 system ? — that the county has an ample development of Upper and 

 Middle, but not of Lower Devonian rocks ? 



Hitherto we have accepted the opinion of Professor Sedgwick re- 

 specting the Petherwin and Barnstaple beds ; namely, that they are 

 strictly contemporary, and constitute the uppermost division of the 

 Devonian system. It may, perhaps, be well, before closing this 

 paper, to go somewhat fully into the arithmetic of the question. 



A glance at Table IX. will show the number of fossil species and 

 genera found in the two areas. 



TABLE IX. 





Petherwin. 



Barnstaple. 





Geu. 



Spec. 



Gen. 



Spec. 





3 



3 



1 



1 



Ecliiiu)ilci-iuata 



1 



1 



4 



6 





2 



2 



1 



1 





2 



2 



3 



3 



Bi-acliiopoda 



7 



20 



8 



26 



LauK'llibrauchiata 



7 



14 



8 



21 





6 



9 



7 



10 





5 



21 



2 



8 





33 



72 



34 



7G 



* Memoii-ij Gool. Siuvoy, vol. i. p. 96. 



