STRATIGRAPHICAL FEATURES. 77 



in this lower portion of the Spiti shales, the fossil remains are less 

 well preserved, and often crumble altogether into small fragments. 



b. The middle horizon of the Spiti shales is similar in lithological 

 character. Fine, splintery black shales, with many ferruginous part- 

 ings and marly concretions which generally yield well-preserved 

 fossils, especially Ammonites. From this level nearly all the " Spiti 

 shale " fossils have been derived. This horizon passes upwards into — 



c. Also chiefly consisting of black splintery shales, but with 

 fewer concretions, and frequently alternating near the top with 

 more regularly bedded black shales and impure limestone. Am~ 

 monites become scarcer in this horizon in Niti, whilst Belemnites 

 and Bivalves predominate. Towards the upper part of this horizon, 

 beds of lighter coloured sandstone in thinner beds are intercalated, 

 and it appears that the Spiti shale formation passes into a series of 

 argillaceous shales and limestones which I have in this memoir included 

 in the cretaceous system. 



The strata of the Spiti shales being generally soft are easily dis- 

 integrated, and have readily yielded to the crushing and folding pro- 

 cess to which the Himalayan systems were and are still subjected. 

 The Spiti shales therefore not only take part in all the grand flexures, 

 but, as is invariably the case where rigid strata alternate with more 

 yielding ones, they have been frequently squeezed into the narrowest 

 folds, and often the rigid cretaceous strata overlying the Spiti shales 

 have been pushed over the latter. Very much disturbed sections of 

 this nature may be seen in the Dharma and Lissar valleys, where all 

 that remains of the Spiti shales are very narrow strips inclosed in 

 crushed folds of the rhaetic and lias. 



The fossils found in this system have so far shown an upper rather 

 than middle Jurassic character; but as most of the material has been 

 derived from the middle and upper division (b and c) of the system, 

 it is quite possible that not only the middle, but also lower jurassics 

 may eventually be discovered in the Himalayas. 



The Jurassic deposits form one of the most widely distributed 



Distribution. Hund^s systems in Central Asia. Wherever I have met 

 and Central Himalayas. them ^ the Centra , Hima i ayaSj they p re sented 



( 77 ) 



