408 MR. A. V. JENNINGS ON THE [Aug. 1899* 



Lareb Station, the railway-cutting shows that the base of the 

 serpentine is almost in contact with the crystalline breccia described 

 above/ (Fig. 4, p. 402.) 



While the lower margin of the serpentine is thus easily seen 

 both near the Parsenn-Furka Pass and at Laret, the conditions of 

 the intermediate country are far less simple. 



The Parsenn area is difficult of study, as it consists mainly of 

 steep grass-slopes with few satisfactory exposures of solid rock. 

 It is, however, evident that the northern edge of the serpentine 

 passes into the zone of ophicalcites, calcareous red-and-green 

 * Schiefer,' which have been described in the foregoing pages. 

 These rocks are well developed round the Mittelalp and along the 

 gorge of the Stutzbach ; they are represented by a narrow band 

 at Riiti and above Monbiel, but cannot be seen in the Laret railway- 

 cutting. Westward they disappear at the Parsenn-Furka Pass, and 

 are only to be rediscovered towards Arosa. 



In the middle of the Parsenn slope the rocks are more distinctly 

 shaly ; true red shales pass into green shales, and these, developing 

 calcareous laminae, form a transition to thin-bedded limestones with 

 argillaceous separation-planes, that one cannot help regarding as 

 belonging to the Mittelbildungen. A little to the east (just 

 above the forking of the Stutzbach) occur detached patches of this 

 group of rocks carried up apparently by the serpentine, and here 

 may be obseryed contorted strata composed of interbedded red 

 shale and limestone. (See fig. 7, p. 407.) 



It appears, therefore, that on the Parsenn slope a secondary 

 infold of the Lower Triassic rocks is present, separated from the 

 qolomite of the Cotechna, but probably identical with the rock 

 under the serpentine on the other side of the Lareterthal, and 

 perhaps once continuous with the well-developed Mittelbildungen 

 of the Haupterhorn on the west. 



Above and north of this narrow outcrop are low rocky crags, 

 composed of brecciated crystalline schists with white granite. The 

 interrelation of these is difficult to make out, but attention may here 

 be called to the point where the general thinning-out takes place 

 above the Schwarzsee Alp. The granite is certainly in contact with 

 the dolomite, and the serpentine follows directly upon it. On the 

 middle of the ridge, and rising as it were from below these crystal- 

 lines, come the red rocks from which the Cotschna derives its name. 

 They are contorted lenticular bands of red hornstone or chert full 

 of radiolaria, passing in a short distance into ordinary red shales, 

 such as were above noted as present in the near neighbourhood 

 interstratified with the shaly limestones. 



The radiolarian cheits do not appear in the railway-cutting at 

 Laret, where only red shales occur between the crystalline breccias, 



^ I am inclined to think that at this junction also the serpentine has been 

 thrust over underlying beds, and crushed against the crystalline breccia. There 

 is, it is true, a different rock at the junction, but it seems more like a crushed 

 dyke- rock, perhaps of the diabase group, than a contact-product: it contains 

 fragments of a yellow limestone. 



