Distribution of the British Ostracoda. 



49 



dental interlopers) except in decidedly brackish water (b), and 

 jet again another, which we may regard as an offshoot from 

 the brackish group, and whose members (c) seem to luxuriate 

 chiefly, though not perhaps entirely, in waters which, though 

 fresh, are subject in some slight degree to tidal influence ; and 

 in cases where these occur apart from the conditions here noted, 

 we should be disposed to conclude either that such occurrence 

 is accidental and perhaps not permanent, or that the local 

 conditions have been materially changed at some not very 

 remote epoch. 



The following lists embrace the typical members of the 

 last-named groups : — 



Cythere porcellanea, Brady. 



gibbosa, B. 8f R. 



Robertsoni, Brady. 



Oytheridea torosa (Jones). 

 Loxocoucha elliptica, Brady. 



pusilla, B. 4- R. 



Cytherura Robertsoni, Brady. 



Group C (subbrackish). 



Cypris incongruens, Ramdohr. 

 Cypridopsis obesa, B. 8f R. 

 Goniocypris mitra, B. Sf R. 

 Metacypris cordata, B. 8f R. 

 Candona compressa, Koch. 



Candida, var. tumida, B. & R. 



Cythere fuscata, Brady. 

 Limnicvthere Sancti Patricii, 



B.^'R. 

 Darwinella Stevensoni, B. 8f R. 



Group A (littoral). 



Cythere badia, Norman. 



rubida, Brady. 



albomaculata, Baird. 



Xestoleberis aurantia {Baird). 

 Cytherura nigrescens {Baird,). 



cellulosa {JVorman). 



Paradoxostoma variabile {Baird) 



pulchellum, G. O. Sars. 



Fischeri, G. O. Sars. 



obliquum, G. O. Sars. 



hibernicum, Brady. 



Group B (brackish or estuarine). 



Cypris prasina, Fischer. 



salina, Brady. 



Cypridopsis aculeata {Lilljebory). 

 Potamocypris fulva, Brady. 

 Cythere castanea, G. O. Sars. 



As regards geographical distribution, the chief fact which 

 we are at present able to point out is the admixture, at the 

 northern extremity of our area, of a distinct glacial or arctic 

 fauna, characterized by such species as Cythere horealis, C. 

 concinna, G. costata^ C. eviarginata^ C. leiodermaj C. mira- 

 bilis, Cytheridea Sorhyana^ G. jjapillosa, and G. punctillata ; 

 while, on the other hand, our southern and south-western 

 shores harbour certain species which do not seem to thrive so 

 well in more northern latitudes, and which are conspicuously 

 absent from our eastern coast : in this list may be mentioned 

 Bairdia injlata^ B. acanthigera, and Gytliere emaciata. Two 

 species which are common in most other districts {Gytliere 

 villosa and Loxoconcha imj^ressa) are also of rare occurrence 

 on the eastern coast, the place of the latter being occupied to 

 a large extent by L. guttata., and of the former by G. lutea 

 and perhaps G. albomacidata. 



Ann. & Mag. N. Hist. Ser.4. FoZ. ix. 4 



