24 CANON NORMAN — THE CELTIC PROVINCE : 



animals which are denizens of the North Sea from the Straits 

 of Dover to the North of Scotland. In a paper on the Shetland 

 Fauna read before the British Association in 1868,* I wrote 

 thus : — " The distribution of animal life around our coasts 

 appears for the most part to have followed the direction south, 

 west, north, east. It would seem that comparatively very few, 

 if any, southern species have made their way north through 

 the Straits of Dover, which may probably be accounted for 

 by the fact that that channel has, geographically speaking, 

 been only a short time open.f As a rule, southern species are 

 to be seen at a higher latitude on the western than they are on 

 the eastern coasts. There are, however, some apparent, but 

 only apparent, exceptions. These consist of animals known on 

 the north-east coast of Scotland, which we should not have 

 expected to meet with there. On examining into the probable 

 cause of their migration to this district, I am led to believe 

 that they have made their way thither round the western and 

 northern, and down the eastern coasts, to their present habitats, 

 and not up the eastern coast as might at first have been 

 supposed. For example, Cerithium perversuvi, Phasianella 

 pulla, Fissurella greeca, Tellina balaustina, Callimiassa sub- 

 terranea, Palmipes placenta, Amphiura hrachiata, etc., have 

 been found in the Moray Firth, but are wholly unknown on 

 the eastern coast of England." During the forty years which 

 have since passed other facts have come to light with respect 

 to certain species and the apparent migrations down the east 

 coast of Scotland and England of some oceanic forms, which 

 greatly strengthened the zoological evidence. 



First, the Arctic naked Pteropod, i.e. a molhisk which swims 

 with a pair of wing-like organs, and which is so abundant in 

 the Greenlandic Seas that it forms no inconsiderable part of 

 the food of the Greenland whale, has occurred on several 

 occasions off the east coast of Scotland. Next, there is 

 a remarkable case of migration southwards of a littoral rock- 

 loving limpet, Acmoea testndinalis. No part of the British coast 

 had been more thoroughly explored than Northumberland. 

 Tet in all their searches, neither Johnston nor Alder nor 

 Hancock had ever seen this mollusk. But in 1856 and 1857 it 

 was met with at the Fame Islands [Tate] and Whitburn [Abbes] , 



* " Shetland Final Dredging Eeport. Pt. II. On the Crustacea, Tunicata, 

 Polyzoa, Echinodermata, Actinozoa, Hydrozoa, and Poiilera," by the Rev. Alfred 

 Merle Norman, M.A., ' British Assoc. Report for 1868.' 



t From what follows the reason given here is perhaps questionable. 



