1869.] GEOLOGY AND MINERALOGY. 351 



The only cases of fossilif'erous boulder clays are those which 

 I shall presently describe under the second type of boulder clay, 

 and which form cliffs upon the shore, and never extend to any 

 distance inland. 



It is difficult to explain these facts in connection with the 

 marine origin of the older biulder clay. 



Upon the higher grounds it occupies frequently large hollows; 

 these hollows might possibly have existed beneath an ice s'lieet 

 and the clay have been accumulated within them, and subjected 

 to great pressure. 



At lower levels the boulder clay is largely developed, both in 

 the pli.ins themselves, and on the flanks of the hills bordering 

 wide valleys, and may thus have been formed beneath the ghicier 

 near its termination at the sea. 



Whatever explanation of its origin, however, may be given, 

 there seems, so far as present investigations extend (and I admit 

 that all present investigations are more or less tentative), to be 

 evidence for the existence of a boulder clay. (1) Older thim the 

 fossiliferous glacial deposits. (2) Extending to greater heights 

 than those to which the proof of any recent elevation in Scotland 

 yet extends. (3) Unsubjected to any action of the tidal' wave 

 upon the shore. (4) And connected with the more remote and 

 extreme arctic conditions. 



II. There is a boulder clay very similar in physical composi- 

 tion to the one just described, but containing fragments of broken 

 shells and many Entomostraca and Foraminifera. 



I have examined this along the Irish coast, at the base of the 

 Hill of Howth, and many other localities ; on the Scotch coast ; 

 on the English coast near Sunderland ; in Yorkshire, and along 

 the banks of the Mersey. 



The shells this boulder clay contains are essentially arctic in 

 character ; but they are very fragmentary, and even single valves 

 are seldom found whole. This feature is in strange contrast with 

 the state in which fossils are found in the great shell beds, resting 

 upon the boulder clay in the Clyde districts. In these shell beds 

 specimens are characteristically found with united valves, and in 

 their natural position. 



I have not yet observed this clay in any other situation than 

 within easy reach of the shore, and I am inclined to regard this 

 fossiliferous boulder clay as peculiar to the seaward terminations 

 of the general deposit. 



