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IX. A Monograph of the Hecent British Ostracoda. 

 By Geoege Stewardson Brady, Esq. Communicated by Dr. Sclater, F.L.S. 8fc. 



(Plates XXIII.-X] J.). 



Read May 3i-d, 1866. 



Since the publication, in 1850, of Dr. Baircl's work on the British Entomostraca, 

 much has been done towards the elucidation of the anatomy and physiology, as well as 

 the distribution and zoological classification, of these animals, and probably no group 

 has received a larger share of attention than the Ostracoda. The interest attaching to 

 this group is much enhanced by the fact that they alone, of all the higher Microzoa, are 

 found in the fossil state in sufficient numbers to afford grounds for any exact comparison 

 betAveen the fauna of the present and those of bygone ages ; and it is, of course, only 

 by the diligent collecting and accurate description, both by pen and pencil, of the forms 

 now living in our lakes and seas, as well as of fossil species, that much progress in this 

 direction can be made. 



The classification hitherto in vogue has rested almost entirely upon external shell- 

 characters and mode of hingement ; and, seeing that by far the greater number of 

 species have been described from fossil specimens, no other method was, of course, prac- 

 ticable. But though the careful study of the shells, which has necessarily accompanied 

 such a plan of classification has been very advantageous, and has, indeed, resulted to a 

 considerable extent in a really natural grouping and arrangement of genera and species, 

 it is obviously an unsatisfactory and unsound basis of classification ; and much has been 

 recently done by various continental authors to increase our knowledge of the minute 

 structure of the animals themselves. Among the naturalists Avho have been foremost 

 in this work may be mentioned Professor Lilljeborg, Eischer, Zenker, and G. O. Sars. 

 The admirable memoir of the last-named author, ' Oversigt af Norges marine Ostra- 

 coder,' published in 1865, contains descriptions of all known Norwegian marine species 

 classified according to the anatomical characters of the animals, the structure of 

 most of which is there for the first time minutely described. This work forms, indeed, 

 an epoch in the study of the Ostracoda ; and its author deserves the warmest acknow- 

 ledgments of all carcinologists for the light which he has thrown, at the expense of 

 much time and labour, on the minute structure and affinities of the creatures of which 

 he treats. To British naturalists the work is, indeed, especially valuable, on account of 

 the close relationship existing between the faunas of the two countries ; and I have, in 

 this monograph, adopted, with but little modification, the arrangement and classification 

 propounded by the author of the ' Oversigt.' The greatest difficulty which I have 

 myself experienced arises from the fact that l)y far the larger number of my deep-sea 

 specimens have been dried in the first instance with the mud or sand in which they were 



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