4 THE VOYAGE OF H.M.S. CHALLENGEE. 



the only impedimeut to universal distribution must probably be connected with tem- 

 perature. So far as yet appears the limits of endurance in these creatures are reached 

 at about 50 degrees south, and 35 degrees north of the Equator. Dr Claus, however, 

 describes a Mediterranean * species, which is either identical with, or very closely allied 

 to Halocypris atlantica, Lubbock. But this habitat, in any case, only very slightly 

 increases its northward range. Next to these Halocyprides, the species which most 

 nearly approach a cosmopolitan character are three Cytheres — Cyihere acanthoderma, 

 mihi, Cythere dictyon, mihi, and Cythere dasyderma, inihi, each of which occurred in 

 five or six of the seven provinces. This statement, however, by no means expresses 

 their ubiquitous distribution in the deep sea, — a fact which only becomes fully apparent 

 when we find that amongst the forty -five lists of dredgings from depths of over 100 

 fathoms, Cythere dictyon is noted twenty-three times, Cythere dasyderma, nineteen 

 times, and Cythere acanthoderma, seven times. Kritlie producta appears in six out of 

 the seven provinces, and is certainly one of the most common of deep-water Ostracoda, 

 but the greater number of the examples grouped under this name consist only of 

 separated valves, varying largely in form and size, and, it may be, belonging to more 

 than one species. The difficulty of dealing with imperfect specimens of shells which 

 possess no distinctive character of sculpture or surface-ornament is insuperable. In 

 glancing over the columns of the tables of distribution, one notes instantly that the 

 Austi'alasian province possesses far more than an even share of species ; the genera 

 Macrocypris, Bairdia, and CytKerella are especially strongly represented there. 

 Out of eight species of Macrocypris this province shows five, of twenty-two Bairdice 

 it has sixteen, and of thirteen Cytherellce ten. One reason for this abundance of 

 species, I believe to be that we have a large proportion of shallow-water dredgings from 

 this province. As to the relations between the Ostracoda of distant parts of the globe 

 and those of the European seas, — or rather of the British and Scandinavian seas, those 

 being the only districts which, as yet, have been tolerably well explored, — some 

 scanty, though interesting observations, may be made. I have, elsewhere, had occasion 

 to note the occurrence at Kerguelen Island of a very common European copepod, 

 Harpacticus fidvus, which in that distant spot inhabits precisely the same sort of 

 places as in Europe. And, now, in the lists of the Kerguelen Island Ostracoda, we 

 may notice an afiinity with the European fauna much closer than that of any other 

 locality coming into the scope of this memoir. The British residents found in this 

 distant home are Pseudocythere caudata, G. 0. Sars ; Sclerochilus contortus (Norman) ; 

 Paradoxostoma abhreviatum, G. 0. Sars ; Krithe bartonensis (Jones) ; Xestoleberis 

 depressa, G. 0. Sars ; and Polycope orbicularis, G. 0. Sars. Some well-known northern 

 forms : Cythere stimpsoni, G. S. Brady ; Cythere tenera, G. S. Brady ; Loxoconcha guttata 

 (Norman) ; Cytheropteron intermedium, G. S. Brady ; and Paradoxostoma ensiforme, G. 



1 Ueljer die Gesclileclitsdifferenzen von Halocyirris, Prof. Dr C. Claup, Zeitsclir. f. wissensch. Zool. Bd. xv. 4 Heft, 1865. 



