2 INFERIOR OOLITE AMMONITES. 



tinguish a certain species from any others, but I shall endeavour to point them 

 out as clearly as possible in my descriptions. I would also draw particular 

 attention to the study of the suture lines of Ammonites, which has, in many 

 cases, been very much neglected, and I hope to be able to give an accurate 

 delineation of those of each species which will come under my notice. 



Geological Chabacters. 



The first point to be considered is the vertical extent of those beds of the 

 Ammonites which I propose to describe, that is to say, the limits of the 

 Inferior Oolite, its commencement and its close. And it is more especially with 

 the former of these questions — whether certain beds belong to the Inferior Oolite, 

 or should be classed as a continuation of the Upper Lias — that we have to deal, 

 since the different development of these, so to speak, intermediate beds in different 

 districts has given occasion for a large amount of writing and a great difference of 

 opinion, and has been the frequent cause of confusion. The subdivision of 

 formations into zones and subzones will most probably help us to more thoroughly 

 elucidate the matter, and leave us with a single point to determine, namely, 

 whether a particular zone shall belong to the Lias or Inferior Oolite. Upon this 

 matter it may be as well to give shortly the opinions of a few authorities. For 

 instance, Dr. Oppel, who studied the whole of the Jurassic rocks in England, France, 

 and Germany, and who was probably the first to separate the various formations 

 into zones, gives in his work, 1 page 305, the Torulosus-bett as the lowest bed 

 belonging to the Inferior Oolite, and underneath he ends the Upper Lias with the 

 Jurensis-bett ; see also his opinion, page 299. Between the Murchisonas and 

 Jurensis beds he places two others, the Trigonia navis bed and the Torulosus bed. 

 These two are now generally united under the name of " Opalinum-zone." 

 Therefore Dr. Oppel begins the Inferior Oolite with the " Opalinum-zone. " The 

 next point to determine is what Dr. Oppel calls the Torulosus bed, and on this 

 point we have his opinion on page 296 of the same work, where he gives a section 

 of Frocester Hill, and there places the upper portion of the Ammonite bed in the 

 zone of Torulosus and the lower portion in the zone of Jurensis, making the 

 division between Lias and Oolite in the middle. So far we have the opinion of one 

 authority as to the proper starting point of the Inferior Oolite in Gloucestershire, 

 and of course according to his decision we should know the beginning of the Inferior 

 Oolite in other parts to be with the zone of Torulosus, provided we can determine 

 the position of the said zone. 



1 Oppel, ' Die Juraformation Englands, Frankreichs und des Sudweatlichen Deutschlands,' 1856 — 

 1858. 



