222 Mr. De la Beche on the Differences 



above alluded to, that these light-coloured Jura-looking lime- 

 stones containing dolomite and gypsum, either belong to some 

 development of the lower part of the green-sand formation, or 

 to the upper part of the ooUte series*. As yet, however, we 

 have no very good zoological evidence to show to which it 

 should be referred, but it would not appear to be any equiva- 

 lent of the zechstein formation of Germany. 



The only other example that I shall at present offer to the 

 attention of the reader, is taken from the environs of La Spezia, 

 which I examined in April last, and is fortunately very illus- 

 trative of a great mineralogical change in the oolite forma- 

 tion. 



On the west side of the gulf of La Spezia there is a range 

 of mountains extending along the coast nearly to Levanto, 

 their breadth augmenting as they advance N.W. The sec- 

 tions afforded by various portions of these mountains are com- 

 posed of the following rocks, easily observed up any of the 

 cross valleys and along the coast from Porto Venere to Monte 

 Rosso. 



1. Limestone Series.! a. Upper beds compact and gray, vary- 

 (the upper rocks.) J ing in intensity of tint, more or less tra- 

 versed by veins of calcareous spur; here and there in- 

 terstratified with schistose beds, and even argillaceous 

 slate. The beds most commonly thick. The variety with 

 light-brown veins, so long known by the name of Porto 

 Venere marbles, forms part of these. 



b. Dolomite; varying in appearance, not unfrequently 

 pure and crystalline, when most so, nearly white, resem- 

 bling, at a distance, statuary marble ; in some places beds 

 may be distinguished, in others stratification cannot be 

 traced. 



c. Numerous thin beds of dark-gray compact limestone. 



* M. Elie de Beaumont is inclined to consider them as referable to the 

 green-sand series. The following note shows the connection of the decided 

 representative of the green-sand and the limestones in question. — Speaking 

 of the rocks in the southern part of the Alps, M. Elie de Beaumont says: 

 " I have not mentioned the small portion of rocks containing numnuilites 

 which advance from the E. of the primitive mountains of L'Oisans to 

 within a short distance of the Monestier de Brianyon. This nummnlitic 

 system is intimately connected with the white compact limestone of Nice, 

 of Proven9e, of the fountain of Vaucluse, of the summit of Mont Ventoux, 

 of the departments of the Drome, the Isere,&c., in which are found num- 

 mulites, milliolites, hippurites, &c., as well as very beautiful oolites. This 

 same system is connected with the fossil deposits of Brianyonnet (depart- 

 ment of the Basses Alpes), of Villard le Lans(Iserc), the mountains of the 

 Grande Chartreuse, of the Mont du Chat, of the hi,i:h longitudinal valleys 

 of the .f nra, of the Perte du Rhone, of Thonne, and of the Montagne des 

 Fis." — Annaks dcs Sciences NaLurcllcs, vol. xv. p. iibO. 



d. The 



