J. Starhie Oardner — Cretaceous Gasteropoda. 105 



next hard bed, thus making the terrace of limestone below extend 

 right up to the face of the scar, which would be formed not only by 

 the limestone and sandstone, but also by the shale, the whole of 

 which would be in the base of the scar. 



If the Glacial Erosion theory of the origin of these rock-terraces 

 is the true one, we ought to find similar features in districts where 

 glaciers now abound, and we should find them especially well marked 

 Avhere a glacier is known to have recently retreated up its valley. 

 I cannot find that any of our noted glacialists have remarked on 

 such features. We read much of rocJies moutonnees, and mamillated, 

 smoothed and rounded surfaces, but nothing of straight lines of 

 scars and flat terraces. Prof. Eamsay says, " The rocks in the valley 

 over which it slides become smoothed and polished — not flatly, but 

 in flowing lines." ^ Hence the sharp edges of the scars and the 

 flatness of the terraces in the Yorkshire Dales tell against the Glacial 

 Erosion theory. 



Features similar to those described so often above can be formed 

 without the help of glacial erosion, for they are found in parts of the 

 world where there are no traces of glacial action. It has been well 

 said by one in replying to somewhat similar views of glacial erosion 

 advanced by the Eev. 0. Fisher and Mr. Mackintosh in former num- 

 bers of this Magazine : — " It is unwise to accept agencies of limited 

 applicability to explain universally occurring phenomena when we 

 have agencies everywhere active, and which are believed, given sufficient 

 time, to be equal to the work performed." ^ 



I had intended criticising the paper on " Coums, Corries, or 

 Cirques," but this article has already run to great length, so I re- 

 frain from doing so here. My purpose is served if I have shown 

 that the argument in favour of the origin of these characteristic 

 features of the Yorkshire Dales by Glacial Erosion is not nearly so 

 strong as it has been represented, and that ordinary Subaerial Denu- 

 dation does not " fail completely " to account for them. 



II. — On Cretaceous GASTEnoroDA. — Family Soalid^. 



By J. Starkie Gtardner, F.G.S. 



(PLATES III AND IV.) 



{Continued from the February Number, page 78.) 



SoALARiA Clementina, Mich. Gault. Plate IV. Figs. 1, 2, 3, 4. 



Shell very elongated, angle less than 10°, composed of eighteen 

 or possibly more elevated, squareish whorls, which slightly diminish 

 in convexity in descending the spire; apex acuminate (Plate IV. 

 Fig. 4) ; ribs ten or eleven, straight or slightly sinuous, linear 

 near the apex, but becoming more prominent and obtuse with the 

 growth of the shell, the intervening spaces nearly flat. Tlie ribs, in 

 common with those of other Cretaceous Scalidge, are never so clean 



^ Phys. Geol. and Geog. of Great Britain, third ed., p. 141. 

 2 Topley, Geol. Mag. Vol. IV. p. 185. 



