XCIV PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



which do not appear in the lower or triasic strata, such as the teeth 

 of Hyhodus, which occur in the middle region of the lower lias of 

 Lyme Regis, whilst in foreign localities some of the remains of Sau- 

 rians occur in the same hand-specimens with Ammonites pl(/7iorbis, so 

 that there is a certain balance of authority on the subject as regards 

 the Vertebrata ; but in respect to the Mollusca, Dr. Oppel observes, 

 that they harmonize best, as shown by Escher von der Linth, with 

 the upper St. Cassian beds, and he thus concludes : — If it cannot 

 be decided with certainty that the bones of Vertebrata found in the 

 bone-bed were originally buried in a deposit of the Keuper, it 

 must at least be admitted that the animals themselves had lived 

 at that period ;" and I may add, only specializing the further re- 

 marks of Oppel, that it would seem impossible to account for the 

 occurrence of such saurian and other remains in the bone-beds of 

 England and Ireland by supposing them to have been removed 

 from a previously existing triasic formation, and then deposited in 

 a liasic formation, as no trace of the Muschelkalk bone-bed has 

 been hitherto found in England and Ireland, unless the bone-bed 

 itself be the equivalent of the Muschelkalk, as I ventured to suggest 

 some years ago, in my Report on Londonderry. 



Der Mittlere Lias, Liasien, or Middle Lias, as representatives of 

 which in England Dr. Oppel adduces Upper Lias Marls of De la 

 Beche, the iron-stone and marlstone of the upper portion of the 

 Lower Lias shales of Phillips, he divides into five zones, character- 

 ized as the zone or bed of A. spinatus, that of A. margaritatus^ 

 which zone he subdivides into an upper and a lower, that of A. 

 Dav(Bi, Sow., a fossil which Oppel himself observed at Charmouth, 

 Dorsetshire ; that of A. Ibex ; and that of A. Jamesoni ; to which it 

 is suggested by Oppel that another, A. armatus, might be added. 

 Der Obere Lias, Toarcien, or Upper Lias, as representatives of which 

 are quoted the Alum-shale, the lower portion of the inferior oolite 

 of De la Beche, the Harley sandstone of Conybeare and PhilHps, 

 the Upper Lias of Philhps and of Murchison, Oppel divides into 

 two great zones, characterized as the zone or bed of Ammonites 

 Jurensis, and that of the Posidonomya Bro?ini. It is not my inten- 

 tion to follow the author into his subdivision of the Unter-oolith, 

 Bajocien, or Inferior Oolite, being the lower of the three sections of 

 Der Mittlere Jura, which is effected upon the same principle, namely, 

 that of adopting some fossil, generally an Ammonite, as characteristic 

 of each of the five subsections into which he divides it. This prin- 

 ciple implies that the actual range in time of each of these fossils 

 has been accurately determined ; but surely such a determination 

 cannot be considered final or satisfactory until the range in space 

 has also been determined ; and further, even supposing the centre 

 of the vertical sections (representing time) through which each of 

 these fossils extends in different countries be actually on the same 

 geological level with each other, can it be expected that the lower 

 and upper limits should also be so, in all countries? I say this, 

 because I fear that, however natural such a system of subdivision 

 may appear, it must at present be considered only artificial, and 



