314 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 9, 



which are limited to the different stages of these great groups. The 

 Liassic Crinoidea and Echinidce are all distinct from those of the 

 Inferior Oolite, and its upper stages Great Oolite, Forest Marble, and 

 Cornbrash. The Echinidce of the lower division of the Oolitic group 

 are all distinct from those of the middle ; and the latter in like 

 manner are distinct from all other Oolitic forms. If this be true of 

 the stratigraphical distribution of the Echinodermata, it follows that 

 the Pea-grit (of the prevailing species of which I have given a list 

 in the description of Crickley Hill, p. 298) must be a very distinct 

 formation from the Cephalopoda-bed, on which it rests, seeing that 

 not one of the twenty species of Echinoidea and Crinoidea found in 

 that rock alone have been discovered in the Cephalopoda-bed a few 

 feet below it ; nor, on the other hand, has one of the twenty species 

 oi Ammonites, Nautili, and Belemnites found in the Cephalopoda- 

 bed been discovered in any of the stages of the Inferior Oolite ; so 

 that both our positive and negative evidence lead us to the conclu- 

 sion that the Cephalopoda-bed marked the close of the Liassic, and 

 not the commencement of the Oolitic formation. 



Place of the Cephalopoda-hed on the Continent. — The Cephalo- 

 poda-bed * forms a very persistent fossiliferous band, occupying the 

 same geological horizon, in France, Belgium, and Germany. My 

 friend Charles Pierson, Esq., of this town, has shown me a small series 

 of fossils which he collected at Croisilles, near Thury Harcourt, Cal- 

 vados, from an Ammonitiferous bed which rests on the brownish 

 marls of the Upper Lias ; the series consists of Ammonites variabilis, 

 Am. Raquinianus, Am. striatulus. Am. radians, and one or two 

 species of Belemnites. This bed is overlaid by the Inferior Oolite, 

 containing Ammonites dimorphus. Am. ParJcinsoni, Trigonia cost at a, 

 Astarte modiolaris, Desh., Pleurotomaria ornata, Def., Pleuroto- 

 maria conoidea, Desh., and Terebratula sphceroidalis ; and is under- 

 laid by the shaly marls, the Upper Lias, containing Am. communis. 

 Am. hifrons, Belemnites elongatus, Mill., and many other shells 

 which he has not preserved. 



M. Terquemf has described the same bed as it occurs in the 

 "departement de la Moselle" under the name " Gres supraliassique 

 ou marly sandstone." This sandstone, he observes, might litholo- 

 gically be confounded with the " gres medioliassique," which appears 

 to be equivalent to our Marlstone, if palaeontology had not indicated 

 the distinction to be made between them. This bed is found near 

 the summit of Saint- Quentin, above Tignomont, in the environs of 

 Thionville, at the summit of the hill of Guenetrange, Saint- Michel, in 

 the environs of Longwy, at Mont-Saint-Martin, at Long-la- Ville, &c. 



* M. Eugene Deslongchamps, in his " Notes pour servir a la Geologie du Cal- 

 vados " (Bull. Soc. Linn. Normandie, 1856, p. 1), has described this bed as No. 9 

 of his section at Evrecy : it is there formed of a slightly coherent, argillaceous 

 limestone, penetrated often with small, ferruginous, oolitic grains slightly adhering 

 together. It contains many fossils, which are not well preserved, as Ammonites 

 opalinus, Modiola plicata, Gervillia contorta, and the characteristic Rhynchonella 

 cynocephala. 



t Extrait de la Statistique de la Moselle, page 22. 



