166 PROE. J. W. JTJDD ON THE OLIGOCENE 



nized on the Continent. It has been shown that, not only in the 

 districts in which its existence was first made known, hut also in 

 Switzerland, Italy, and Hungary, deposits are found, sometimes 

 attaining a thickness of several thousands of feet, which contain 

 the same well- characterized fauna, and must be referred to the same 

 division of the geological series. And by the labours of Beyrich, 

 Yon Konen, Sandberger, Mayer, Yon Hantken, and many other 

 palaeontologists our knowledge of the extent and peculiarities of the 

 fauna has been greatly enlarged. 



The marine fauna of the Hempstead beds unquestionably agrees 

 in the closest manner with that of the Fontainebleau Sandstone, the 

 Rupelian of Belgium, the marine sand of the Mayence basin, and 

 the clays of Hermsdorf, Cassel, &c. in JS'orthern Germany. All of 

 these strata are now recognized as belonging to the Middle Oli- 

 gocene. 



The Brockenhurst beds contain a rich fauna, the analogues of 

 which, as we have seen, are not found in the Paris basin (where 

 the strata of this horizon are of freshwater origin), but which find 

 their exact representatives in the Lower Tongrian of Belgium and 

 the Clays of Lattorf, Egeln, and Helmstadt in Northern Germany. 

 These constitute the Lower division of the Oligocene. 



With regard to the beds which underlie the Brockenhurst series, 

 those, namely, of Headon Hill and Hordwell Cliff, there is equally 

 little room for doubt. They unquestionably represent the " Zone 

 of CeritMum concavum" which was long ago recognized as exist- 

 ing in the Paris basin by Prof. Hebert, and of which the import- 

 ance has been more recently demonstrated by Dr. C. Mayer and 

 Prof. Sandberger. On one point some little difference of opinion 

 may still exist — namely, as to whether the strata of the Zone of 

 CeritJiium concavum should be placed in the Eocene or Oligocene. 

 As we have already pointed out, a study of the marine forms which 

 they contain proves that the fauna is intermediate between those of 

 the Barton and Brockenhurst series. Both Dr. Mayer and Prof. 

 Sandberger incline to the view that they should be grouped with 

 the Bartonian, and regarded as an upper member of that division. 

 In this country, on the other hand, as also in the Paris basin, the 

 evidence appears to me to point in the other direction, and I can- 

 not but regard this Zone of Oerithium concavum as the base of the 

 Oligocene — a view which is shared by Prof. Beyrich himself. As a 

 matter of fact, the fauna of the beds in question is so strictly inter- 

 mediate in character between the Barton and the Brockenhurst 

 faunas, that it may be regarded as a question of convenience 

 whether they should be grouped with one or the other. In this 

 country there can be no doubt that convenience demands that they 

 should be grouped with the other fluvio-marine beds. 



In dealing with the classification of the Oligocene strata of the 

 Hampshire basin it is desirable to retain as far as possible the local 

 groupings which are already familiar to geologists, only making 

 such corrections as the new facts discovered concerning the succes- 

 sion of the strata prove to be absolutely indispensable. 



