DISTRIBUTION OF SPECIES. 



117 



§ VIII. SUMMARY OE EACTS OE DISTRIBUTION. 



1. Freshwater and Ifarine Species. — Of the one hundred and thirty-two species of 

 Ostracoda described in this Monograph, twenty-four may be considered to have been 

 inhabitants of fresh or shghtly brackish water, the remaining one hundred and eight 

 being strictly marine species. The freshwater group is constituted as follows : 



Cypris cinerea. 



— compressa. 



— gibba. 



— ovum. 



— reptans. 



— salina. 



— virens. 



— Isevis. 

 Cypridopsis Newtoni„ 



— obesa. 

 Candona albicans. 



— Candida. 



Candona eompressa. 



— detecta. 



— lactea. 

 Potamocypris fulva. 

 Darwinella Stevensoni. 

 Limnicythere antiqua. 



• — inopinata. 



— monstrifica. 



— San cti-Pat rich . 

 Cytheridea lacustris. 



— torosa. 

 Loxoconcha elliptica. 



Of these twenty-four species all except one {Limnicythere afitiqua, respecting which 

 we entertain some doubt as to whether it may not be a sexual variation or a stage of 

 growth of some other species) are perfectly familiar to us as inhabiting at the present 

 time the freshwater ponds and rivers or the brackish littoral pools of Great Britain 

 and parts of the European continent. Two of them seem to be much restricted in their 

 distribution, and have been found fossil only in the neighbourhood of the localities where 

 they still live : these are Cypridopsis Newtoni and Darwinella Stevensoni. The presence 

 of Cytheridea torosa or Loxoconcha elliptica may be taken as an almost certain indication 

 of more or less brackish water ; it is seldom that either species is found living in quite 

 fresh or in undiluted sea- water. 



The distribution of the marine species is, however, much more perfectly known : 

 their number being so much greater, and the area over which tliey have been studied so 

 much wider, we are thus better able to recognise in their distribution the effects of 

 climate and other physical conditions. A comparison of the Ostracodal fauna of the 

 Scottish glacial clays with that of the seas at present washing the European shores leads 



