Environs of Lons le Saunier. 133 



these beds is from 15 to 20 centimetres [6 to 8 inches] ; the 

 limestone presents itself as two diiferent species ; it is grey, 

 compact, with a splintery fracture ; or else it is yellow 

 brown, with an unequal and earthy fracture ; in the former 

 case, the stony matter of the shells loses itself in the paste 

 enveloping them, so that they can with difficulty be distin- 

 guished ; in the second case, on the contrary, the rock is a 

 yellow limestone, from which the shell is distinguished by 

 a chesnut brown colour ; I could discover on the surfaces 

 that had long been exposed to the air, some perfect shells of 

 the genera mytilus and venus, some striated pectens and 

 buccina. Before the variegated marls are quitted, subordi- 

 nate beds are found of a compact whitish argillaceous lime- 

 stone, of a very fine paste ; then the solid beds of gryphite 

 limestone are met with, the name of which I have taken for 

 the entire formation.* 



■ * The gryphite characterizing this limestone, and the Jura Chain, as 

 well in the parts I have visited, as in those from which I have received 

 specimens, is the gryphaea arcuata, (Lam. An. sans vert. ed. of 1818. 

 Knorr. P. 2. pi. Ix. fig. 2. Gryphaea incurva. Sowerby, pi. cxii. fig. 1 

 & 2. Parkinson's Org. Rem. pi. xv. fig. 3.) The gryphaea cymbium 

 much resembles it, and perhaps belongs to the same formation ; but I 

 have not observed it in the Jura, properly so called, I have found it in 

 an analogous rock on the coast of Normandy, from Havre to Dives. M. 

 von Schlotheim appears to have confounded under the denomination of 

 gryphites cymbium, the arcuata and cymbium ; but they are, notwith- 

 standing their resemblance, two distinct species. The question is here 

 only of the gryphaea arcuata, as determined by the good figures of it 

 above cited ; it is the only one I have found in the Jura, properly so 

 called. I have recognised it in many other places, such as the environs' 

 of Avalon in Burgundy, near Bayeux and Valognes in Normandy, at 

 Cheltenham in England, &c. and always in rocks that resemble each 

 other in their nature, their position, and the other shells accompanying 

 them. 



Note by the Translator. — It is almost needless to remark that the gry- 

 phaea incurva, as well as ammonites Bucklandi, mentioned in a subse-i 

 quent note by the author, as found in the gryphite limestone, are charac- 

 teristic shells of the lias, and that the rock at Cheltenham is lias, and \ 

 can also state that those near Bayeux and Valognes, in which this shell 

 is found, are the same. 



