

1865.] Note velating to Sivalik Fauna. 65 
represented vertebrate faune, occurring in a series of beds, closely 
related in point of geological conditions of deposit, ete., and yet 
distinctly separated (broken) in time. 
The application of the fact to stratigraphical geology may now 
take shape. The strata at the base of the sections visible in parts of 
the Sivalik hills are representations of the Nahun group—the middle 
group of the Sub-Himalayan series. The expression of this on a map 
must still be arbitrary : for the true Sivalik strata (though so strongly 
unconformable with the ‘ Nahun’ strata along their junction with the 
inner zone of these Nahun rocks,) appear to pass conformably and 
even by gradation into the representatives of the Nahun strata in the 
outer zone. It is of course to be expected that a very close study 
will reveal traces of this unconformability in the sections of the 
Sivalik hills also; but in such massive, banked strata, from twenty to 
two hundred feet thick, the determination of such a feature will be 
very dubious. 
In physical geology this feature will be only another example, on a 
larger scale than those given in my Memoir, of the supposition I have 
offered in explanation of the mode of disturbance of all these Sub- 
Himalayan rocks—slow contortion and upheaval along narrow zones 
synchronously, with more or less. uninterrupted deposition in the ad- 
joining exterior area. 
