44 



EEV. K. B. WATSON ON THE GREAT DRIFT-BEDS WITH SHELLS 



been founded to determine the length of time during which the sea stood at the 

 forty-foot terrace-line, and so on. Now, admitting the obvious fact of the 

 destruction of the rock at many points of our present sea-line, it yet appears that 

 on the whole the influence of the sea in modelling the land in recent times has 

 been very small. In a great many cases it has not so much as penetrated the 

 boulder-clay ; and even where that has been washed away, as in the coast of the 

 Little Cumbrae, figured and described by Mr Smith of Jordan Hill, in his " Newer 

 Pliocene Geology," p. 144, the striations of the rock remain with wonderful fresh- 

 ness. From all this it is obvious that the terrace lines of the basement rock are 

 not due to the action of the present sea, but were given to it previous to its sub- 

 mergence. 



In short, we find that all the latest geological changes, with their accompani- 

 ment of river and sea-action, have not materially modified the face of the country 

 — the rock skeleton of which was moulded finally under the glacial epoch.* 



List of the Shells found in the Ahran Beds, with the Depths at which they live on 



OUR OWN AND THE NORWEGIAN COASTS, AS GIVEN BY FORBES AND HaNLEY, AND BY 



Danielsen. 



Name. 

 Balanus crenatus. 



] 



Panopoea norwegica. 



Tellina balthica, (a brackish variety of 



Solidula.) 

 Cyprina islandica. 

 Astarte elliptica. 



arctica. 



compressa.f 



striata (a variety of compressa .) 



British. 

 Deep water to 50 fathoms. 



Deep water to 90 



Shore. 



5-80 

 10-40 



80 (dead) 

 7-70 



Norwegian. 



Not known living. 



20-60 fathoms. 



20-40 „ 

 20-60 

 10-80 „ 

 10-40 



* I cannot let this paper go without expressing my obligations for much information and many 

 suggestions to my friend Mr Geikie's valuable paper on the Phenomena of the Drift. I am grati- 

 fied to agree with him on the land origin of the material which constitutes the boulder-clay, and on 

 the subsidence of the land during the formation of the boulder-clay. On some other points, too, I 

 think we are not very far from an agreement, though I fear we differ fundamentally on many of the 

 most important. 



f I only found one specimen of this species. The shells were partially crushed, but the two 

 valves were united, and retained both epidermis and ligament. Mr Searles Wood, who was good 

 enough to examine it for me, says it is one he does not recognise. Mr S. P. Woodward, who has 

 also taken the trouble of looking at it, considers it an unusually large A. compressa of the variety 

 striata. It is one-third larger than even the excessively large specimens of the species from the 

 Red Crag, figured by Mr Searles Wood in his Bivalves of the Crag. — {Pal. Soc. Fab., vol. ii. p. 

 184, pi. 16, fig. 8, a and c.) 



