2 Messrs. G. S. Brady and D. Robertson on the 
Probably more extended investigation may add to the number 
of species, but it is evident that “the fauna of salt marshes is a 
very restricted on 
That of eivasectubtion; on the contrary, embraces, amongst 
the Microzoa to which we now refer, a very large number of 
species, some of which are evidently derived from the fresh- 
fossiliferous don we should at once infer "that the strata 
must have been edm in water subject more or less to 
marine influences. Of this group the principal members are 
Cythere castanea, G. O. Bets. Cytheridea torosa (Jones) and 
its varieties, and Loxoconcha elliptica, Brady; scarcely less 
marked in their preference for brackish water are Cypris sa- 
lina, Brady, Cypridopsis obesa, B. & R., C. aculeata (Lillje- 
borg), Potamocypris fulva, Brady, Cythere D AE x & R., 
Cythere porcellanea , Brady, Loxoconcha pusilla, B. & , Cy- 
therura flavescens, Brady; C. Robertsoni, Brady Os is 
(Norman), and Paradoxostoma Fischeri, G. 0. 
species commonly resident in fresh water we notice 
twelve, the most frequent of which are Cypris levis, Müller, 
compressa, Baird, gibba, Ramdohr, Candona candida, Müller, 
lactea, Baird, and Limnicythere inopinata (Baird) ; while of 
those usually found in the sea, but not unfrequently spreading 
plentifully up into estuarine localities, we bond name Cythere 
m ucida, Baird, tenera, adus albomaculata, Baird, viridis, 
eee villosa (G. O. Sars), Xestoleberis oe, (Baird), 
xoconcha tamarindus e ones), Cytherura nigrescens (Baird), 
eata, Brady, striata, G. O. Sar ars, angulata, Brady, Cytheri- 
dis subulata, Brady, Paradoxostoma variabile (Baird), abbre- 
viatum, G. O. Sars, and ensiforme, Brady. The total number 
of Ostracoda known to us as inhabiting tidal rivers and their 
estuaries, excluding those found in the Norfolk district, of 
which we shall speak separately, is eighty-six. 
From this enumeration and from the accompanying cent 
it will be seen that the genera Cytherura and Paradoxostom 
