Dr. Wheelton Hind — The Yoredale Series. 209 



but be noted that it is totally different from that of the Mountain 

 Limestone, and also of the Yoredale Series of Wensleydale ; and the 

 question at once arises as to the correctness of applying the term 

 Yoredale to them, seeing that they differ so essentially, both litho- 

 logically and palseontologically, from those beds to which the term 

 was originally applied. There is in these beds an absence of the 

 limestones which are so characteristic of the series in Wensleydale, 

 and this may at first sight appear to account for the difference in the 

 faunas ; but, as a matter of fact, some of the shales in Wensleydale 

 are far richer in organic remains than the limestones, and these 

 remains are typically those which occur in the great mass of 

 limestone. 



Indeed, if my contention be correct, that the Yoredale Series of 

 Wensleydale is the homotaxial equivalent and also the chronological 

 representative of the massif of limestone so typical of Derbyshire, 

 then the black shales of North Staffordshire, Derbyshire, and South 

 Yorkshire belong altogether to a higher horizon and are not in any 

 way the equivalents of any beds of the Yoredale Series. If strati- 

 graphical division be necessary, the only reliable data, in the absence 

 of unconformity or some well-marked change of lithological character, 

 are of a palfeontological nature ; and this evidence points undoubtedly 

 to a closer biological connection between the so-called Yoredale Beds 

 of Derbyshire with those above, and the Yoredale Beds of North-West 

 Yorkshire with those below. It appears to me that the so-called 

 Yoredale Beds of Derbyshire and Yorkshire should really be 

 included in the Millstone Grit Series, as they contain a very similar 

 fauna and flora, and, moreover, certain very well developed sand- 

 stones, often extremely difficult to separate on lithological grounds 

 from true grits. 



There are three very different molluscan faunas in Cai'boniferous 

 rocks, and I have j'et to be convinced that they are actually 

 intermingled in the same bed, though there can be no doubt that 

 they overlap each other somewhat. 



No. 1. — The Coal-measure fauna, rich in fish-remains, with the 

 molluscan genera Carhonicola, Anthracomya, and Naiadites ; 

 essentially a fresh-water fauna. 



No. 2. — The Lower Coal-measure and Grit fauna, the Gannister 

 and Grit Series, largely marine, but littoral ; Aviculopecten, 

 Posidoniella, Goniatites, Orthoceras, Nautilus, and peculiar 

 Gasteropoda. 



No. 3. — The Limestone fauna, essentially marine, rich in corals, 

 Polyzoa, very rich in Brachiopods ; with Pecten, Avicula, 

 Edmondia, Sanguinolites, and many other genera of Lamelli- , 

 branchs, Gasteropods {Euomphalus, Pleurotoinaria, Murchisonia, \ 

 Loxonema, etc.), and Cephalopoda, Corals, Crinoids, and Eish- 

 remains, m.any of these being peculiar to certain beds. 



In a few localities, as at Congleton Edge (vide p. 207), we find 

 a curious fauna, which would appear to be a mixture of a few 

 of the Brachiopoda of the Limestone with a fauna on the whole 



DECADE IV. VOL. IV. — NO. V. 14 



