REPOET ON THE OSTRACODA. 3 



traces of the existence of living Ostracoda. In by far the greater number of cases the 

 specimens consist of detached valves, or of perfect, though empty, shells. When any 

 vestige of the soft parts remained it was carefully examined, and three new genera, 

 Phlyctenophora, Bythocypris, and Crossophorus are here described as a result of such 

 investigation ; some little new knowledge has also been gained of the characters of other 

 genera. Still, as a whole, the results of the Challenger's work in this department are 

 disappointing. I had thought it possible that in this, as in other departments of 

 zoology, forms might have been found connecting our own age more distinctly than has 

 hithei-to been done, with bygone geological epochs, or, even more probably, showing new 

 and remarkable variations of structural type. But these anticipations have in no way 

 been realised. Amongst the marine Ostracoda of the British Islands alone we have 

 at least thirty different genera represented. The whole of those brought home by the 

 Challenger are distributed amongst twenty-eight genera, the British genera absent from 

 the Challenger lists being Potamocypris, SarsieUa, Darivinella, Eucytkere, Brady cinetus, 

 and Conchoscia. But the comparison is scarcely, in this form, a fair one. The work 

 of the Challenger gave us no collections whatever from between tide marks, nor from 

 the laminarian zone, and these two zones usually swarm with microzoic life of all 

 kinds. The genus Paradoxostoma, in British seas, is almost exclusively a littoral one, 

 and it is in this zone that many memljers of other genera attain their best develop- 

 ment. I do not doubt that shore-collecting in the tropical and sub-tropical seas would 

 yield rich results to a student of the Ostracoda ; and it has this great advantage over 

 the dredge, that specimens are readily obtained liAang and unmutilated. 



Geographical distribution may most readily be studied by dividing the area explored 

 into several districts, arranging under each the species met with within its limits. With 

 this view I propose to divide amongst seven areas the whole of the Challenger explorations : — 



1. North Atlantic Ocean (Stations 1 to 110 and 348 to 354). 



2. South Atlantic Ocean (Stations 111 to 142 and 313 to 347). 



3. South Indian Ocean (Stations 143 to 160). 



4. Australasia, including the coasts of Australia, New Zealand, and the Eastern 

 Archipelago south of the Equator (Stations 161 to 196 and 217 to 220). 



5. South Pacific Ocean (Stations 271 to 312). 



6. North Pacific Ocean (Stations 238 to 270). 



7. Eastern Asia, including China, Japan, and the Eastern Archipelago north of tlie 

 Equator (Stations 197 to 216 and 231 to 238). 



A glance at the table of distribution wiU show that only two Ostracoda are found 

 pliant enough to live in all of these seven areas ; these are two natatory pelagic species.. 

 Hcdocypris atiantica, Lubbock, and Hcdocypris hreviostris, Dana. The reason of this 

 wide distribution is sufiiciently clear ; to animals living mostly near the surface of the 

 sea, and dependent, probably, upon no restricted or specially localised supplies of food^ 



