ON GEOLOGICAL NOMENCLATURE. 357 



To return to the sub-divisions of the Tertiaries, the smaller of the 

 Sub-apennine or Pleiocene epoch are taken from the names of 

 places in Italy with rich fauna, showing different ages. 

 The (Eningen beds have, generally, been accounted TJ. 

 Meiocene. Prof. R. remarks that his two periods in the 

 Tertiary correspond with the Upper and Lower Tertiaries of 

 Karl Mayer who is undoubtedly a great authority : still these two 

 divisions are not separated by a hard line. If the geological record 

 was complete there would perhaps be no lines to be di-awn at all 

 except conventional ones. In the L. Tertiary we find our London 

 and Barton clays and Thanetsands giving names to three sub- 

 divisions. 



Professor E. has not divided the Cretaceous into Upper and 

 Lower, though he admits it might be replaced by two periods ; it 

 has however been so divided by Lyell in later editions that the one 

 cited and by other English authors. Remarks are made on the 

 different values given to the Neocomien group ; Professor R. uses 

 the word in the more restricted sense and separates from it the 

 Aptien, Rhodanien and Urgonien which are probably the 

 equivalents of part of our L. Greensand beds. 



The Jurassic group is divided after the manner usual in English 

 classifications, into Lower, Middle and Upper. The Lower 

 including the Bath freestone and accompanying beds from the so- 

 called Inferior Oolite to the Combrash ; the German method is to 

 include the Lias in the Lower Jurassic, against which are many 

 reasons. As Bradford-on-Avon is so near to us we are interested 

 to notice that it forms one of the divisions of the fourth column . 

 the Bradford Clay with us is a band less than 10 feet thick and 

 therefore hardly worth making into a separate division ; it may be 

 considered as a clay band of the Forest Marble, a local featui-e; it is 

 at the base where it does occur, and forms a convenient point of 

 separation between the Bath Oolite proper and the Eorest Marble, 

 but its characteristic fossil Apiocrinus Parkinsoni is found equally 

 in the Eorest Marble, and the clay itself dwindles down to almost 

 nothing in places. The Bradfordian of the Table however 



