165 



From an investigation of the fauna of the Middle Lias, it 

 would appear that the Asteriada3 and Ophiuridse are found in 

 greater numbers in this division of the Lias than any others, 

 a fact which, perhaps, may be accounted for on the supposition 

 that these beds were Httoral formations. 



lY. — ToAKCiEN otr Lias Supeeiettb. 



When M. A. d'OitBiGNr substituted the phrase etage Toarcien 

 for Upper Lias, he had in view the town of Thouars, Toarcium 

 (Deux Sevres,) in the vicinity of which he had seen one of the 

 finest sections of this formation, and which he regarded as its 

 best French type ; and for that reason I shall give it in detail 

 here. 



Lias sttpeeieue, Thouaes, (Deux S^ivees)''^ 



a Thick bed of very white argillaceous Limestone, containing Silex, 

 with Belemnites tripartitus. 



h Ferruginous Limestone and clay, with Ammonites Jurensis, Ziet. 

 Alternate beds of blue clay and Limestone passing in the 

 upper portion to a ferruginous clay, with Ammonites insignis, 

 Schub., and Belemnites irregularis. 



c Blue Clay with Ammonites radians, Schloth. , Am. variahilis, d'Orb. , 

 Belem. tripartitus. 



d Grey granular Limestone, with Ammonites Tliouarsensis, d'Orb. 



e Compact Limestone, without fossils. 



/ Thin band of ferruginous clay, with Ammonites serpentinus, 

 Schloth. 



g Thick bed of sandy Limestone, worked for building stone. 



h Foliated saccharoid Limestone, with Ammonites bi/rons, Brug. 



i Thick bed of yellowish Limestone containing grains of Quartz, 

 and forming the basement bed of the section. 



In other departments of France the Toarcien attains a 

 considerable development, as in Cher, Lozere, and Aveyron, 

 where some of the sections have a thickness of nearly 500 feet. 



* Cours Elementaire de Paleontologie et Geologic Stratigraphique, tome II., 

 p. 469. 



