OF THE SWISS JURA AND ENGLAND. 



257 



other hand, absent from the 4 Fer sous-oxfordien,' but is recorded 

 from the overlying beds in the Jura. From these considerations it 

 is clearly seen that the ' Fer sous-oxfordien ' is represented by the Ox- 

 ford Clay of England ; but whether the former represents the whole 

 of the latter is very difficult to decide. The ' Fer sous-oxfordien ' 

 undoubtedly contains several species which occur in our Lower and 

 Upper Oxford Clay ; but some characteristic fossils of the latter 

 subdivision are absent, and have been found only in the beds over- 

 lying the ' Fer sous-oxfordien,' and it is quite possible that a portion 

 of the Oxfordian beds of the Jura may be the equivalent of the 

 upper part of the Oxford Clay of England. 



In our southern district of the Jura it will be remembered that 

 the Callovian is but feebly developed as compared with that of the 

 northern area. Jaccard's list of fossils {op. cit. p. 213) from these 

 beds includes 11 species of Ammonites (some beloDging to the cordati 

 and others to the ornati group) nearly all of which occur in the 

 Oxford Clay of England. Amm. macrocephalus is not recorded, 

 nor is Gryphcea dilatata. The representatives of our Kelloway 

 Kock and Oxford Clay, or at least the greater part of them, must 

 be found in these Callovian beds. 



The fauna of the Oxfordian beds in the northern part of the Jura 

 is fairly well marked off from the underlying Callovian, indeed it is 

 much more closely allied to the Corallian. Out of the 154 species 

 recorded from these beds (Greppin, op. cit. p. 68) 55 pass up into the 

 ' Terrain a chailles siliceux,' whilst only 13 occur in the Callovian. 

 Amongst the 154 species there are no less than 51 English species 

 coming from the following horizons * : — 



Lower Oolites , . . 2 species. 



Oxford Clay . 3 „ 



Corallian (including the Lower Calcareous Grit) 23 „ 



Oxford Clay and Corallian 21 „ 



„ „ and Cornbrash 1 „ 



Kimeridge Clay . . 1 „ 



51 



The species peculiar to our Oxford Clay are : — 



Ammonites crenatus, Brug. 



flexuosus, Munst. 



Terebratula impressa, v. JBuch. 



And such forms as Amm. perarmatus, Amm. cordatus, Amm. convo- 

 lutus, and Gryphcea dilatata are also present, which in England 

 range from the Oxford Clay to the Lower Calcareous Grit. The 

 evidence derived from these fossils supports the view already ex- 

 pressed, that a portion of the Oxford Clay of England is on the 

 horizon of the Oxfordian of the Jura. 



* In working out the range of the English fossils the following lists have 

 been used :— Morris's Catalogue of British Fossils; Hudleston, i'roc. Geol. 

 Assoc. vol. v. p. 481 ; Blake & Hudleston, Q. J. G-. S. vol. for 1877 ; Sedgwick 

 Essay for 1886, MS. 



