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Guide to Belfast. 



coast of Antrim. The coast offers all degrees of exposure 

 and shelter, from North Antrim, open to the Atlantic, to the 

 land-rocked lough of Strangford. Bathymetrical conditions 

 are also varied : the water deepens to 70 or 80 fathoms in 

 most places, while off Rathlin Island a rocky depression sinks 

 to 133 fathoms. The seas of our district are the coldest 

 in Ireland, and the mollusca have a distinctly northern facies, 

 some 36 species being unknown or very rare north of Britain, 

 while about 18 have a southward range. Of the northern 

 shells, Acmcea (Tectura) testudmalis^ Emarginula crassa, 

 Trichotropis borealis, Trophon dathratus^ Nuculana (Leda) 

 mifiuta, and Crenella decussata have all been taken alive in 

 our waters ; while of the southern forms Circulus striatus 

 {Troc/ius Dumi/iyi), Lunatia {Naticd) sordida, Ovula patula, 

 and Barbatia (Area) lactea will serve as examples. The 

 most remarkable features of the area are the very exten- 

 sive and northern fauna, made up chiefly of dead shells, 

 of the Turbot Bank, which lies in about 30 fathoms off 

 Belfast Lough ; and the surprising richness of the 15 to 17 

 fathom ground discovered by Dr. Chaster's party inside of 

 Rathlin Island, where a single day's dredging yielded one 

 species new to science and two more new to Britain. 



In estimating the total fauna, it is difficult to state figures 

 exactly, as doubt exists whether a few of the Turbot Bank 

 shells should not rather be classed as quaternary fossils. 

 But leaving these doubtful items out of account, we may 

 reckon the moUuscan fauna at 330 species, made up as 

 follows : 



Cephalopoda 



Amphineura 



Gastropoda 



Scaphopoda 



Pelecypoda 



9 

 9 



190 

 2 



120 



Total ... 330 

 The Irish moUuscan fauna (o-ioo fathoms), reckoned 

 similarly, totals about 470 species, to which are to be added 

 67 species more, which are confined to the deep-water 

 district (100-1,000 fathoms), which zone may be considered 

 as unrepresented in our area. 



