42 BRITISH DEVONIAN BRACHIOPODA. 



Sp. Urii is exceedingly common in the shape of casts in the brown grits of Marwood, 

 Barnstaple, and Brannton, in Devonshire ; and it occurs also in what Mr. Salter considers 



vantageously dispensed with ; that the lower portion of the strata representing the Siluro-Carboniferous 

 interval should be given to the Silurian, while the upper portion, including the Petherwin, Marwood, and 

 Pilton beds, should form part of the Carboniferous system. The strong notion of the equivalency of the 

 Devonian and Lower Carboniferous is growing up in some quarters, as well as that of a close affinity and 

 representativeness of the Devonian and Carboniferous forms ; but such views are far from having been 

 hitherto satisfactorily proved. At the time I first began my researches among the Brachiopoda, I believed 

 to some extent, along with many others, in the supposed independence of geological systems ; but, as I pro- 

 gressed with my geological and palseontological studies, I gradually began to doubt the existence of any 

 absolute palseontological demarkation between any contiguous geological systems, and was led to concur with 

 M. De Verneuil, who attaches less importance than do many geologists to those geological and palseontological 

 divisions of the crust of the globe, which he believes to be more in our idea than in nature, and conforming 

 more to the actual state of science than to its complete development. I therefore hasten to declare, that 

 I do not consider the Devonian formation to be an independent system any more than I do the Carboni- 

 ferous and Permian ; all three appearing to me to be connected by a gradual passage of certain species. 

 I am, therefore, quite prepared to admit that a certain number of Brachiopoda have passed from what is 

 termed Upper Devonian into Lower Carboniferous ; and some species from the other classes are common to 

 the two periods; certain bivalved Entomostraca, for instance, are declared by Mr. R. Jones to be identical, 

 &c. But for all that, if for nothing else but the sake of convenience and reference, I should feel disposed 

 to retain the divisions introduced by Sir R. Murchison and other geologists, when deprived of the fallacious 

 idea of their absolute independence. 



Mr. J. Beete Jukes informs me that he considers the Carboniferous Slate of Cork to be absolutely con- 

 temporaneous with the Carboniferous Limestone of the rest of Ireland, and that the Marwood and Pilton 

 grits of North Devon are also the sandy representatives of the Carboniferous Limestone, and therefore not 

 Devonian at all. The study I have recently made of some of the Brachiopoda collected by Mr. Jukes 

 and the Irish Geological Survey, in the slaty and sandy beds which lie between thick Carboniferous Limestone 

 and genuine Old Red Sandstone at Scariff, and in other localities in the county of Cork, would lead me 

 to agree with Mr. Jukes that these brown grits and slates may be contemporaneous with or equivalent 

 to the North Devon, Marwood, and Pilton beds, whether they be considered as Upper Devonian or as 

 Lower Carboniferous. They possess several fossils in common, such as Spirifera di.y'uncta, Sp. cristata, 

 var., an Athyris, probably referable to A. concentrica, Rhynehonella pleurodon, and some species of Orthis, 

 Chonetes, and Productus, to be hereafter described. The nature, however, of these fossils, as well as the 

 presence of Cyrtina heteroclita, associated with Spirifera disjuncta in the grits of Reenydonegan Point, at 

 the head of Bantry Bay, would make me pause awhile prior to recognizing these beds to be, strictly speak- 

 ing, Carboniferous, or until it may have been satisfactorily proven that what geologists have hitherto 

 considered as Upper Devonian should in reality form part and parcel of the Carboniferous. Mr. 

 Jukes informs me, moreover, that the beds at Reenydonegan Point, which contain so interesting an 

 assemblage of what 1 should consider Upper Devonian and Carboniferous Brachiopoda, is up near the top 

 of what he terms the Irish Carboniferous Slate, or 4OU0 or 5000 feet above the top of the Old Red Sand- 

 stone, and that they are full of Phillipsia pustulosa, the common Carboniferous Trilobite, and other fossils, 

 apparently common Carboniferous species. These Irish and North Devon grits would therefore, on 

 palseontological grounds, seem to be intermediate beds, connecting the Devonian with the Carboniferous; 

 for there can be no doubt that, taken as a whole, the fauna of the Devonian formation is distinct from that 

 of the Carboniferous, although the two formations may be connected by a gradual passage and mixture of 

 Devonian and Carboniferous species ; or, in other words, it is no doubt the truth that there are certain 

 species of fossils common to Devonian beds and the Carboniferous system ; but it is not the whole truth, for 



