120 Report of the Magnetic Survey of India, [No. 2, 



Northward, and in the Northern part to the Southward. It is only 

 with some hesitation that we venture to bring forward this opinion. 

 Our observations during next summer in a part of the Western 

 Himalayas, and of Ladak, must show whether this structure can be 

 considered a general one or not. 



Sedimentary Strata. 



16th. In the sedimentary strata, which, as it has long since been 

 ascertained, compose the northern flanks of the Himalayas, we 

 met with — 



(1) The silurian and devonian formations, the latter being cha- 

 racterised by the appearance of numerous large and long-winged 

 spirifera ; and (2) the trias with several ammonites, closely allied to 

 those which characterise the trias of the Alps, and the Jurassic 

 formations. The latter is divided stratographically into two great 

 groups, the lower one composed of black and bluish slates and marls, 

 containing in many places large numbers of well-preserved ammo- 

 nites, the upper group consisting of limestones and marly lime- 

 stones of different colours, which seem not to contain any ammonites 

 but are very often full of bivalve shells, comprising small and large 

 oysters, pecten, a very characteristic and common species of Astarte, 

 a Trigonia, which we think will not be distinguishable from the 

 wide-spread Trigonia costata, found also, if we recollect rightly, in 

 Cutch, &c. 



Amongst the numerous ammonites which we had occasion to 

 collect in the lower group from different localities, we found nothing 

 which would indicate an age as old as the lias.* They all are of 

 forms which characterise, in Germany and England, about the 

 middle part of the Jurassic formation. "Whether the lias formation 

 exist in these parts or not, is a question which as yet we are not 

 quite prepared to decide. 



We have no books at hand to examine as minutely as necessary, 

 some small fossil remains of pentacrinus and terebratula, which we 

 found in such a stratographical position, that they may perhaps 

 belong to this formation. 



* The collections made by Captain R, Strachey in 1848, were, we believe, the 

 first which showed clearly that the ammonitic deposits were younger than the lias. 



