6Q2 PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



an assertion, arising from or through similarity, not identity, in rock- 

 masses, without any physical or palseontological proof whatever. 

 "When it is proved, determined and admitted that all the slates, grits, 

 and limestones to the south of, and that rest upon, the Upper Old Pvcd 

 Sandstone of Pickwell Down, are of Carboniferous age, and not 

 Upper Devonian, then these 84 species may occupy the place assigned 

 to them, or be classed with the Irish Carboniferous Slates and their 

 associated Grits. I have, however, good evidence to the contrary, 

 and will not confound either the two areas (Korth Devon and South 

 Ireland) or the species occupying them*. 



Whatever views may be entertained relative to the contempo- 

 raneity of the Carboniferous Slate, either with the Carboniferous 

 Limestone or the Upper Devonian, it is quite evident that in the North 

 Devon area the succession of the strata and of the groups of associated 

 fossils is continuous and natural — being, in fact, one great physical 

 and zoological group. It is only south of the Baggy, Marwood, and 

 Croyde zones, in the order of succession, that we see anything ap- 

 proaching the physical and zoological conditions of the Carboniferous 

 series. The assertion that these beds are Carboniferous Slate with 

 Coomhola Grits, is not borne out by the lists of fossils intended to 

 convey that impression in Professor Jukes's paper f; the Baggy 

 and Croyde series conformably overlie the upper red sandstone of 

 Yention, which constitutes the natural base to the Upper Devonian 

 of North Devon, these being still succeeded at Barnstaple &c. by 

 the Lower Carboniferous beds, which are of great thickness before 

 they reach the Culm-measures to the south. 



I have clearly shown in these Tables the relations that the 

 Upper Devonian fossils of Baggy, Marwood, Sloly &c., have to 

 the Carboniferous in this and other areas; and Mr. Jukes's list, 

 when divested of the 84 species from the Upper Devonian of Pether- 

 win and the above-named places, tells the same facts. 



VI. Steatigeaphical Value op the Species cohpeisixg the 

 Devoniajs" Pauista. 



No one disputes either the intermediate position of the rock- 

 masses comprising the so-called Devonian system, or that, accom- 

 panying them, there is also a fauna composed of genera and species 

 at present not known either below, in the Silurian system, or above, 

 to a very large extent, in the Carboniferous. 



I propose to briefly discuss the evidence and value of this fauna, 

 which will aid us in aJfixing a value to the whole system, and also 

 enable us to distinguish it from the Carboniferous, which, although 

 allied to, and containing many species (54) in common with the 

 Devonian, is yet a totally distinct group ; it is chiefly through its 

 upper division, and at the close or passage into the Carboniferous, 

 that the relation exists, which we should expect. 



* Consult Table X. p. 674. 



t Notes for a comparison between the rocks of the south- west of Ireland and 

 those of North Devon and of Rhenish Prussia (Journ. Rov. Gfeol. Soc. Ireland, 



1865). 



