48 Messrs. Brady and Robertson on the 



V. — Contributions to the Study of the Entomostraca. 

 By Geoege Stewardson Beady, C.M.Z.S., and David 



EOBEETSON, F.G.S. 



No. VI. On the Distribution of the British Ostracoda. 

 [Plates I. & II.] 



We propose in the present paper to give (1) descriptions of a 

 few new or imperfectly known species, (2) catalogues of some 

 recent gatherings which present points of interest, and (3) a 

 summary of our present information as to the distribution of the 

 known British species of Ostracoda. Upwards of three years 

 have now elapsed since the publication of the " Monograph of 

 the Recent British Ostracoda" in the ' Transactions of the 

 Linnean Society ; ' and during that time, by the assiduous 

 working of old fields, and the occasional investigation of new 

 ones, many new species have been added to our list, and much 

 valuable knowledge has been gained as regards geographical 

 and bathymetrical distribution. But the papers * in which 

 these results have been published being much scattered, and 

 perhaps sometimes inaccessible, it seems desirable to present 

 them here in a condensed form. 



Of the one hundred and ninety-nine species now known as 

 inhabitants of the British Islands and their adjacent seas, some 

 six or seven may be said to stand on a rather precarious basis, 

 having been admitted on the strength of one err two specimens 

 only, perhaps " waif and stray," or for some other reason being 

 imperfectly understood. In this category may be mentioned 

 Cypris elliptica^ C. Joanna, Argilloecia cylindrica, Cythere 

 borealis, C. mirabilis, C. marginata, Cytheridea incequalisy and 

 possibly a few others. The whole may be broadly grouped 

 under two heads, comprising the inhabitants respectively of the 

 sea and of fresh water. But among the purely marine forms it 

 is of interest to note that some are strictly littoral (a) in habitat, 

 while others almost exclusively affect considerable depths of 

 water; there is, again, a small but well-defined group, the mem- 

 bers of which are scarcely ever to be found (setting aside acci- 



* The papers here summarized are as follows : — " A Monograph of the 

 Recent British Ostracoda," Trans. Linn. Soc. 1868. "Last Report of 

 Dredging amongst the Shetland Islands " (by the Rev. A. M. Norman), 

 Brit. Assoc. Report, 1868. "Notes of a Week's Dredging in the West 

 of Ireland," Ann. & Mag. Nat. Hist. 1869. " On the Ostracoda and Fora- 

 minifera of Tidal Rivers," ibid. 1870. " The Crustacean Fauna of Salt 

 Marshes," Nat. Hist. Trans. North. & Durham, 1868. " On Entomostraca 

 taken chiefly in Northumberland and Durhaih, in 1869," ibid. 1870. "A 

 Review of the Cypridinidae of the European Seas," Proc. Zool. Soc. 1871. 



