PRELIMINARY REMARKS. 3 



that after a careful investigation of the locality, I was unable to convince myself of the 

 real position of these beds. The shells do not appear to have lived on the spot in which 

 they are found ; some of the Brachiopoda are undoubtedly found in the Tourtia, the Upper 

 Green Sand, and the Lower Green Sand of many localities. Among these we may mention 

 Ter. depressa (Lamarck), a Tourtia shell occurring likewise in the Hils. Cong, of Essen, at 

 least I have a specimen from the last-named locality, undistinguishable from the Tourtia 

 species. Ter. oblonga is found at Farringdon, in the Lower Green Sand of Hythe, 

 Maidstone, &c, in the Hils. Cong, of Essen, and in the French Terrain Neocomien, but 

 Mr. Cunnington has found it also in the Upper Green Sand of Warminster. Ter. sella is 

 abundantly distributed in the Lower Green Sand of many localities, and is met with at 

 Warminster in the Upper Green Sand. R. lata (Sow.) is likewise common in the same 

 conditions, &c. 



It is therefore difficult to decide the question of the age of the Earringdon beds by the 

 Brachiopoda; and I am convinced (notwithstanding M. D'Orbigny's efforts to prove the 

 contrary) that several of the Cretaceous Brachiopoda lived in more than one of his divisions, 1 

 and consequently were possessed of a much greater vertical range. There is no reason 

 why certain forms that lived while the Lower Green Sand was in progress of deposition, 

 should not have existed also in the Upper Green Sand. All preconceived systematic views 

 should be avoided, and it is advisable in the present state of Palaeontology not to imagine 

 that all species were restricted to such narrow limits. The Tourtia of Belgium reposes 

 everywhere directly upon the Palaeozoic rocks ; some consider it a distinct formation in the 

 Cretaceous System. M. D'Orbigny states it to belong to his Stage cenomanien ; M. Dumont 

 supposes it Neocomien, and M. de Koninck, from its containing the Ammonites varians, 

 and other fossils of the Craie chloritee, sup., refers it to that age ; and it is perhaps repre- 

 sented in England by the Chloritic Chalk with green grains at Chard, the Upper Green 

 Sand, and the red chalk of Norfolk. 



1 Consult a most interesting paper by M. J. Cornuel, bearing for title ' Catalogue des Coquilles de 

 Mollusques Entomostraces et Foraminiferes du Terrain Cre'tace inf. de la Haute Marne, avec divers Obser- 

 vations relatives a ce Terrain,' (' Bull, de la Soc. Geol. de France,' vol. viii, 2d ser., p. 430, 1851.) 



In page 446, that author states : — " II est done constant qu'il y a passage de quelques cephalopodes 

 aussi bien que quelques gasteropodes et lamellibranches, des couches neocomiennes dans le Gault. Cette 

 circonstance n'empeche pas la faune du Gault d'etre, dans son ensemble, tres distincte de celle du terrain 

 neocomien. 



"M. le Dr. Fitton a etabli, par la comparaison des fossiles que toutes les couches du gres vert inf. du 

 bassin de Paris y compris le terrain neocomien proprement dit, ne sont autre chose que le lower Green Sand 

 d'Angleterre. Ce savant place la limite superieur du lower Green Sand en Angleterre et en France au point 

 ou commence le Gault. II ne peut rester de doute chez nous qu'au sujet des sables et gres jaunatres et du 

 sable vert (No. 14 et 15 ci-dessus), en ce sens seulement qu'ils paraissent former le passage entre le terrain 

 neocomien et le Gault proprement dit," &c. 



