84 



POST-TERTIARY ENTOMOSTRACA. 



visit, a considerable portion of the occipital bone, with the condyles, foramen magnum, 

 and pterygoid process of a large Cetacean had been found. 



6. The same fine sand continued to the surface, and was broken by a second shell-bed, 

 nearly two feet in depth, and extending along the section in a regular and persistent line. 

 This shell-bed must have been deposited after the Cetacean stranded in the hollow of the 

 Boulder Clay, since it is unbroken in regularity, and has not been disturbed subsequently 

 to its deposition. 



The shells have not been roughly heaped up, as a drift, by wind and tide, since many 

 perfect specimens, fresh as when they were first interred in the sand, were obtained from 

 the bed. Tellina tenuis was extracted with both valves entire, together with numerous 

 perfect examples of Mactra mhtruncata. This second shell-deposit indicates a less depth 

 of water than the one preceding. Its contents consisted of such species as M. suhtruncata, 

 Tellina tenuis, whose special habitat is the sand in shallow water, while from the lower 

 bed were obtained Cyprina Islandica and Lutraria elliptica, which range to greater average 

 depths. 



The rough stones of the lower bed gave place to the finer sands, and the waters 

 becoming more shallow through the gradual elevation of the land, the nature of the 

 characteristic fauna slightly changed during the process. 



The lowest shell-bed is possibly of the same age as the Pecten maximus bed of 

 Colintraive and other localities ; but, however this may be, the fact of the occurrence of 

 distinct beds of shells of undoubtedly post-glacial character proves the necessity for their 

 separate description and examination, and establishes the fact that a series of gradual 

 changes took place in comparatively recent times. 



The following Ostracoda were found : 



Cyth ere jmlliicida, Baird . 



— lute a, Miiller. 



— convexa, Baird. 



— albomaculata, Baird. 



— villosa (G. O. Sars). 



— emaciata, Brady. 

 Cytheridea elo7igata, Brady. 

 Loxoconcha impressa (Baird). 

 Cytlierura nigrescens (Baird). 



— undata, G. 0. Sars. 

 Paradoxostoma variabile (Baird). 



( 



