446 Prof. E. Forbes's Reply to Prof. A. Leymerie. 



Trigonia scabra of Lamarck, M. Leymerie has misunderstood 

 Dr. Fitton's list. That list was given to show that many of 

 the supposed new Neocomian fossils of France were only well- 

 known Lower Greensand fossils of England, some, no doubt, 

 known under names to which they had no claim, but not the 

 less Neocomian on that account ; the Trigonia is an instance. 

 The shell which has hitherto figured in British lists as Tri- 

 gonia scabra is certainly the Trigonia caudata of Agassiz, a 

 Neocomian species. The French conchologists say that the 

 T. scabra of Lamarck is a different shell. Be it so; the case is 

 not changed, though the name scabra in our lists must be re- 

 placed by that of caudata. 



So much for the palaeontological objections of M. Leymerie. 

 Permit me now to add a word on the general question*. 



It may be stated briefly as follows : — Dr. Fitton holds that 

 the formation intermediate between the Wealden and the 

 Gault, known in England as the Lower Greensand, is syn- 

 chronic with the Neocomian of Neufchatel and I'Aube. 



M. Leymerie holds that the Neocomian (ifnot all, the greater 

 part thereof) is synchronic, not with the English Lower Green- 

 sand, but with the freshwater deposit of the Wealden. 



Tested palccontologically, I maintain Dr. Fitton's view is 

 right, not merely from a closer examination of specimens, but 

 also from careful investigations made in the field in conjunc- 

 tion with my friend Captain Ibbetson. This view is also held 

 on natural-history grounds in England by Mr. Morris, in 

 France by M. A. d'Orbigny, and at Neufchatel by Prof. 

 Agassiz and M. Dubois de Montperreaux. The doubts thrown 

 on it by M. Leymerie, I conceive, have been removed by the 

 statements put forth in this reply ; for even were my names 

 wrong (which 1 do not admit), the species to which those 

 names were applied are undoubtedly identical with French 

 Neocomian forms. 



Tested geologically, the hypothesis of M. Leymerie (or 

 rather of M. de Beaumont, whom he follows), that during the 

 deposition of the Wealden there must necessarily have been 

 a corresponding deposit in France, which, ifnot a freshwater 

 deposit, must have been marine, and that the Neocomian is 

 such deposit, cannot stand for two reasons : — 



* In the discussion which followed the reading of M. Leymerie's paper, 

 M. d'Orbigny is reported as saying, that whilst he differed from M. Ley- 

 merie on the geological question and considered the Neocomian and Lower 

 Greensand as identical, he agreed with the author as to the value of the 

 determinations of Dr. Fitton's fossils. Yet it will be seen from what I have 

 stated above, that out of the eight " especes contestees," seven were iden- 

 tified with French species by M. d'Orbigny himself! There must be some 

 mistake in the report, or M. d'Orbigny must have a very short memory. 



