INTRODUCTION. ix 



M. Bosquet's elaborate Table 1 of the distribution of the French and Belgian species 

 refers to the Upper, Middle, and Lower Tertiaries of those countries respectively ; but, 

 as the " Lower Tertiaries " therein indicated do not necessarily include the Lower 

 Eocene, which is but sparingly exhibited in France, it has been requisite, for the sake 

 of comparison, to work out the serial position of the several deposits in which the 

 species of Ostracoda found in England occur also on the Continent ; and the result is 

 given in Table IV in the Appendix. 



Tables V and VI in the Appendix will assist the reader in remembering the 

 relations of the English and the Continental Tertiary deposits. Table VI comprises 

 some of the latest corrections introduced by Mr. Prestwich, to whom geologists are 

 greatly indebted for important information on the correlation of the Tertiaries of 

 England, France, and Belgium. 



I have prefaced the descriptive portion of the Monograph with as complete a 

 general notice of the zoological characters of the animals whose carapaces are under 

 consideration, as the means and time at my disposal have allowed me to do. I regret 

 that the minute anatomical research is almost denied to me now by impaired eyesight : 

 nor have I been enabled, for the same reason, to fully examine the " lucid spots " in 

 the carapaces, as I once intended. 



In a zoological point of view, the species about to be described offer us some 

 interesting peculiarities in the structure of the carapaces and in their hingement and 

 ornamentation. Geologically, it is interesting to observe that considerable uniformity 

 in the distribution of certain species, and of groups of closely allied species, obtain in 

 England and the neighbouring European districts. Several forms belong exclusively 

 to the Middle Eocene, and some are confined to the Lower Eocene, or to other strati- 

 graphical series. On the contrary, some species belong to several deposits of different 

 ages, and of wide geographical range, — such as Cythere {Cytheridea) Mulleri and 

 C. {Bairdia) subdeltoidea, which latter is found from the Cretaceous to the recent 

 period. 



I sincerely thank Mr. George West for the beautiful illustrations he has produced 

 of these remains ; — often obscure and always minute, they have taxed his skill and 

 patience ; and I owe him much, too, in the elucidation of many points of structure 

 which would have been indifferently noticed had he not, with the eye of a naturalist 

 and geologist, worked out obscure characters at the expense of much time and labour. 



In figuring the specimens I have placed the carapaces and single valves with the 

 anterior end upwards ; this being the most convenient, when carapace-remains only 

 have to be represented. It has therefore to be borne in mind that the upper and 

 lower borders of the carapace-valves are right and left in the figures. 



1 'Descript. Entom. Terr. Tert.,' p. 134, &c. 



