^Zoological Characters in Geology. 253 



other in the order of superposition, as tiiey successively pre- 

 sent themselves ; and that they are not portions of the upper 

 parts which have slid down, and have been placed before 

 the lower portions, and finally to be sure that we do not 

 give as two series of beds that which only forms one. 



It was necessary to state the above in order that the fol- 

 lowing enumeration may not be regarded as a perfect list of 

 the succession of the beds. But even with all the inaccuracy 

 that may be attributed to it, it will not the less present the 

 different rocks which compose the southern side of the Mon- 

 tague des Fis, and the comparative results which we may 

 derive from them. 



The hill (G) opposite this mountain, that on which is situ- 

 ated the village du Mont (H), and which is separated fiom the 

 body of the mountain by a small valley in which the Nant de 

 Siouve (E section ; pi. 9) flows ; a hill which may either be 

 the base of the mountain, or independent, and the result of 

 the slide of one of its parts, is composed of black grey wacke 

 slate (No. 1), containing spherical nodules. These nodules, 

 which are a little harder than the rest of the rock, some- 

 times contain impressions of ammonites in their interior. 

 (No. 2). That which I found was too incomplete to deter- 

 mine the species to which it belonged, but it appeared to 

 me very different from the ammonites of the summit of which 

 I shall presently speak, whilst it bears a great resemblance 

 to the ammonite I have mentioned (in the memoir above 

 cited) which comes from an alpine mountain of Oberhasli, 

 of an analogous nature to this transition portion of the Mon- 

 tague des Fis. 



The beds of this slate dip towards the N. as do those of 

 the mass of the mountain. After having passed this species 

 of out-work and the small valley which separates it from 

 the Rochers des Fis, we arrive at the foot of the rocks, and 

 the precipitous escarpments they present, which would ren- 

 der this side of the mountain inaccessible, but for the fallen 

 masses which have there formed very steep slopes, composed 

 of large pieces of rock, always ready to fall, but which can 

 however lead us to the summit. 



