10 POST-TERTIARY ENTOMOSTRACA. 



Between these beds also and the older Boulder Clay shell beds have been discovered. 

 The following section occurs along the banks of the Cloinid burn, near Lag Arran.^ 



^ 1. Surface soil. 



2. Upper drift of sand and stones . . . variable thickness. 



3. Compact bed of stones with little sand 



4. Upper drift of sand and stones 



5. Dark sandy bed with open texture 



6. Stony clay bed, with Arctic shells . 



7. Boulder Clay . 



In this section we may see in regular and ascend 



5 to 6 ft. 



variable thickness. 



4 to 5 ft. 



7 to 10 ft. 



12 to 20 ft. 



ng order — 



An older Boulder Clay (I of this paper, p. 3), unfossiliferous and typical. 



A fossiliferous clay (III of this paper, p. 7) ; a wash from an older bed, with a 



scattering of striated stones. 

 A younger series of clays, sands, and gravels (IV of this paper, p. 8) ; unfossiliferous 



(in this case), loose and sandy, and retaining some feebly striated stones. 



Prom the diverse characteristics of the deposits now described, and which have all 

 been included more or less generally under the terms — Till, Northern Drift, Boulder 

 Clay, it is evidently of the utmost importance that precise descriptions of the clays in 

 which Ostracoda and other fossils have been discovered should be given. Employing a 

 vague nomenclature, a species may be said to occur in the Boulder Clay, and yet have 

 been found either in the second or third or fourth of the beds discriminated in this paper ; 

 or a species may be said to occur under the Boulder Clay, and have been found under the 

 first or the fourth. 



A fossil really belonging to the age of the Paisley Clay might thus, for example, be 

 ascribed to a more remote or a more recent era almost ad libitum, to the great confusion 

 of any attempts to understand either the variations of climate or the distribution of species 

 which may have taken place during the Glacial Epoch and the subsequent physical 

 history of Great Britain. i 



1 Bryce, 'Arran,' &c., p. 185. 



