316 Dr Ch. Martins on the Marks of Glacial Action 



land was more arctic than it now is. He has thus fur- 

 nished us with the zoological proof of the ancient exist- 

 ence of glaciers in this country. Immediately beneath the 

 boulder clay, there is found in many localities on the Frith of 

 Clyde a laminated clay which contains shells. Sometimes, 

 as at Paisley, for example, this clay also contains pebbles. 

 Mr Smith, and, after him. Professor Edward Forbes, have 

 recognised that the most part of these shells appertain to 

 a truly arctic Fauna. Mr Smith even assisted me in 

 gathering a certain number of these shells at Helensburgh 

 and Paisley, and has presented me with others collected in 

 different localities. He has also submitted them to the exa- 

 mination of M. Deshayes, who has authenticated nearly all 

 of Mr Smith's determinations, and established the arctic 

 character of this Fauna.* I give this list as an abridged 

 example, and refer the reader for the additional particulars 

 to the complete enumeration of the species which Professor 

 Edward Forbes has inserted in the Memoirs of the Geological 

 Survey of Great Britain, vol. i., p. 406. 



The most Common Arctic Shells of the Laminated Clay. 



Myatruncata, i., var. udevallensis ; Saxicava Sulcata, var. 

 udevallensis, Sm,; Tellina calcarea, G^?w.; Astarteborealis, i^.; 

 Astarte Arctica ; Cyprina islandica, L. ; Mytilus umbilicatus ; 

 Pecten islandicus, Muller ; Fissurella noachina ; Littorina 

 littorea, X.; Littorina castanea ; Fusus Scalar if orm is, Gould; 

 Buccinum undatum, L. ; Natica clausa ; Balanus sulcatus, 

 Larn. 



Let us now observe how the presence of arctic shells in an 

 upper bed of clay, of boulder clay, or even throughout its 

 thickness, may be explained. Let us return, then, to Spitz- 

 bergen. Here the glaciers descend to the very verge of the 

 sea, bringing along with them striated pebbles, glacier mud, 



* These shells must not be confounded with those which are found upon the 

 terraces, or ancient sea-beaches which so much surround the coast of Scotland. 

 These are identical with the present species living in the sea. One may easily 

 verify this statement close by the Granton quarries, where the terrace is 20 feet 

 above the sea. These terraces prove that the coast has been elevated since the 

 termination of the glacial epoch. 



