1]8 



POST-TERTIARY ENTOMOSTRACA. 



us to conclude that the general character of the glacial Ostracoda is of a type decidedly 

 more boreal in character than that of the present epoch in the same latitudes. Perhaps, 

 indeed, we should not be far wrong in saying that the species found in the clay beds of 

 the south of Scotland correspond very closely with what we should expect to find now 

 living on the Atlantic sea-bed between Scotland and Greenland. It is, however, only 

 from very fragmentary observations made by private effort over the latter area that we 

 are able to draw this conclusion ; and we, therefore, the more regret that the splendid 

 opportunities of research which were within our grasp, during the cruises of the 

 " Lightning " and " Porcupine," seem to have been in this department almost or entirely 

 neglected. Amongst the contents of the clay beds here referred to we are able, never- 

 theless, to point to the following species as extending southward, at the present day, only 

 to latitudes corresponding to those of the Northern Hebrides, and apparently reaching 

 their full development only towards the Arctic regions, or on the western side of the 

 Atlantic, in the cold waters of Canada. 



2. List of Post-Tertiary Species noio known as characterizing the Arctic seas and the 

 northern coasts of Norway, Scotland, and America. 



Cythere leioderma. 



— costata. 



— mirabilis. 



— latimarginata. 



Cytheridea Sorbyana. 

 Cytheropteron inflatum. 

 — angulatum. 



Cytheridea papillosa, C. punctillata, and Cythere concinna, though extending 

 somewhat further southward, and living even abundantly on the eastern shores of 

 England, so far south as Yorkshire, are still conspicuously absent from more southern 

 latitudes. These three species are, perhaps, in numbers, the most abundant of 

 all the glacial Ostracoda. On the other hand, certain species, such as Bairdia 

 inflata, B. acanthigera, and Cythere emaciata, which now are found living most 

 abundantly on the southern shores of the British Islands, becoming rare or altogether 

 absent from the northern shores, are likewise either entirely absent or of extreme 

 rarity in the glacial clays ; nor, indeed, have we found in these clays any species of 

 distinctly southern type. So far, however, as our present limited knowledge of the 

 English Post-tertiary beds extends, it would seem that their fauna indicates at least as 

 much difference between them and the corresponding Scottish deposits, as exists at 

 present in the seas of the two districts. Of the species comprised in this Monograph 

 nineteen are either extinct or have not yet been seen living. They are as follows : 



