POST-TERTIARY POSSILIFEROUS DEPOSITS. 61 



Cythere tuherculata (G. O. Sars). 



— Dunelmensis (Norman). 

 Cytheridea papillosa. Bosquet. 

 • — pundillata, Brady. 

 Loxoconcha tamarindus (Jones). 

 Cytherura niyrescens (Baird). 



— undata, G. 0. Sars. 



— striata, G. O. Sars. 

 Cytheropteron latissimiim (Norman). 



— anyidatum, Brady and Robertson. 



Bythocythere simplex (Norman). 

 SclerocJiilus contorfus (Norman). 



17. Loch Gilp. 



The burn in the excavated banks of which the shell-clay is found begins in the 

 marshy ground west of Baden farm-head. When this burn was deepened shell-bearing 

 deposits were brought to view at several points along its course, variously overlain by 

 gravel, peat, and surface-soil, to the depth of five to ten feet. 



Directly beneath the shell-clay is the Boulder Clay, with the following characteristics : 



1. It is very hard and compact, and tinged with the bluish hue of the surrounding 

 trap -rocks. 



2. It is exceedingly irregular in thickness, and curves violently within a few yards. 



3. The boulders are chiefly schist and greenstone, and very far-travelled ; they are finely 

 striated, smoothed, and polished. 



4. It does not contain the slightest vestige of a shell. 



This Boulder Clay rests upon greenstone rock, striated in horizontal or partly dipping 

 grooves. 



It is not succeeded by the usual laminated clay of the Clyde beds. A remarkable 

 shell-bed rests immediately upon the Boulder Clay. 



The line of junction between the shell-bed and Boulder Clay is sharp and well defined. 

 There is no merging of the shell-bed into Boulder Clay, and no gradual transition. The 

 separation is sharp, and in every way decisive. 



Scarcely at any two places where the shells appear is the composition of the deposit 

 alike. Some portions lose by washing about 10 per cent, and others about 60 per 

 cent. 



In some parts there is a thick blue clay ; in others, a mixture of clay and sand, 

 varying from a sandy clay to a clayey sand. 



