1899] THE BIPOLAR HYPOTHESIS 349 



bipolar hypothesis has been rejected by Professor Herdman for the 

 Tunicates, by Professor Ludwig for the Holothurians, by Dr. Ortmann 

 for the Crustaceans, and that his own analysis has not revealed a 

 single species of fish, of Decapod, of Isopod, of Amphipod, which in- 

 habits at once the arctic and antarctic oceans. 



He admits that the " bipolar hypothesis " might still find support 

 if it could be shown that similar and truly allied forms gave to the 

 two regions a common facies. But of this he finds no convincing 

 evidence. 



Eocene Sharks and Skates. 



The Selachian fauna of the Eocene period is very imperfectly known. 

 There are a few complete skeletons in the fissile limestone of Monte 

 Bolca and Monte Postale in Northern Italy, and a nearly complete 

 skeleton of Xiphotrygon, which was described by Cope, from the Green 

 River marls of Wyoming. In other localities they are represented 

 merely by portions of dentition, detached teeth, cartilage, or vertebrae. 

 As, however, detached fragments are not always distinctive, and the 

 generic or specific assignation of them is little more than guesswork, 

 we are unable to restore the Eocene Selachian fauna from present 

 materials ; Mr. Smith Woodward, however, in the Proceedings of the 

 Geologists' Association for February, has brought together the available 

 evidence from British deposits, and placed it on record in the hope 

 that further search may lead to better material and more accurate 

 knowledge. A plate of fossil teeth accompanies the paper. 



Radiolaria in Devonian Rocks. 



The discovery that Eadiolaria were to be found in the older cherts has 

 been taken up and worked for all it is worth by Dr. J. G. Hinde, who 

 has again contributed a paper to the Geological Society. The present 

 specimens come from the district of Tamworth, New South Wales, and 

 are found in siliceous limestones and volcanic tuffs. Those in the 

 tuffs are better for study than those in the limestones, because they 

 occur more isolated. At present the hunting of fossil Eadiolaria 

 seems highly exciting, and comparable to that of insects, for every one 

 found appears to be a new species, and provides for endless ingenuity 

 in the coining of new names. But, as Dr. Hinde truly says, " our 

 present knowledge of Palaeozoic Radiolaria is limited to those occurring 

 in a few outcrops in Central and Northern Europe," and so rounds off 

 his fifty-three new specific names. 



