216 :E. D. Wellhum—Fish Fauna of Millstone Grit. 



by the highest Litorina beach. The elevation consequent on that 

 is still going on.* And it is not too rash to predict that these 

 oscillations will continue until the ever- weakening effect of the 

 impulse given by the land-ice is neutralized by the other terrestrial 

 factors that produce land-oscillations.- 



From the foregoing pages it appears that " the Post-Glacial geology 

 of the Baltic Sea and the Gulf of Bothnia" stand in the closest 

 relation to their Glacial geology. Therefore I have been unable to 

 make the former clear without at the same time throwing some 

 li2:ht on the latter. 



VI. — On the Fish Fauna of the Millstone Grits of 



Great Britain. 



By Edgar D. Wellburn, L.R.C.P., F.G.S., F.R.I.P.H., etc. 



Introduction. 



ON June 10th, 1898, whilst on an excursion with the Yorkshire 

 Geological and Polytechnic Society, I found three specimens of 

 fish remains in the Millstone Grits at Summit in Lancashire. 

 Subsequently, on several occasions, I again visited the district 

 and succeeded in collecting a large number of fish remains, and on 

 these, together with a few other specimens which had been found 

 in these rocks at rare intervals, I have based the following paper. 

 General Eemarks. 

 Brief Description of the Millstone Grit Bocks. 



The Millstone Grit rocks may be naturally grouped into three 

 divisions, viz. : (1) the Kough Eock at the top; (2) the Kinder or 

 Pebble Grits at the base ; with (3) between them the Middle Grits, 

 which are composed of thick beds of shales alternating with bands 

 of grit rock. The Middle Grits may again be subdivided into four 

 groups, viz., A, B, C, and D beds, A being the uppermost. 



The great Pennine Anticline, between Lancashire and Yorkshire, 

 is mostly composed of these rocks, and on the Lancashire side, 

 south-west of Walsden, at the head of the Calder Valley, there are 

 on the south side several splendid exposures of these rocks ; in 

 one quarry near Summit, Lancashire, there is a very good section of 

 the D beds of the Middle Grits, and in the shales near the base there 

 are a number of nodular masses composed of impure limestone ; 

 it is from these nodules that I have collected the majority of the fish 

 remains. 



The nodules are of peculiar conformation, and vary in size, 

 many being 24: inches in length, 18 in width, and 9 or 10 inches 



* Each successive swing was naturally not only less extensive but shorter than the 

 preceding. From this it may be inferred that the Litorina depression prevailed 

 a shorter time than the Ancylus depression. 



^ Here, of course, it is only Scandinavia that is alluded to. But the same remarks 

 are largely applicable also to North America, although it is not unlikely that the 

 North American ice-sheet, being much larger than that of Scandinavia, melted later 

 than it. In that case the Post-Glacial epoch must have been shorter in North 

 America than in Europe. Herein may lie the reason why many North American 

 geologists, in their estimates of Post-Gflacial time, have arrived in harmony at such 

 low figures as 7,000 to 10,000 years — a far shorter time than that in which the 

 Post-Glacial deposits of Scandinavia were formed. 



