PERMIAN SYSTEM. 5^ 
ciently numerous or sufficiently characteristic to warrant any exact 
correlation. 
The overlying beds (the Productus shales) have been represented by 
Dr. Noetling as containing two distinct cephalopod zones in Spiti, viz., 
a lower with Xenaspis carbonaria, and an upper with Cyclolobus old- 
haini. This subdivision is apparently due to some slight misapprehen- 
sion, for, so far as is known at present, there is one and only one am- 
monite-bearing zone in the Productus shales, and this is situated about 
30 feet below the top. All the ammonites hitherto found occur in this 
one zone, which consists of a string of concretions, and its total thick- 
ness is not more than one foot. 
It has already been stated that the Productus shales and cal- 
careous sandstone are found in all permian sections in Spiti and 
Bashahr, but the underlying beds down to the lowest beds of the car- 
boniferous (or devonian) limestone are very frequently absent, nor are 
they known to occur in any other part of the Himalayas. In lower Spiti, 
and again at the head of the Spiti river, they are found in their fullest 
development, and in both areas the carboniferous limestone and the 
Fenestella shales have been found. The Fenestella shales are well 
exposed in the hills behind Losar. 
Judging from the manner in which the younger palaeozoic beds thicken 
out again in upper Spiti, it is probable that thev 
Probable represen- ^ ' , . 
tatives of the Po will be found also to the north, in the valley of the 
series in Kashmir. ^^^^^ Chandra river in Lahaul and in Kashmir. 
In fact, a great area has been mapped by Mr. Lydekker in that area as 
Panjal ", but from his descriptions of that system, it is possible that 
it may include a considerable part of the shale and quartzite series 
now known to be most probably of upper carboniferous age. The 
slates, quartzites and sandstones described by him,* as exposed on the 
southern side of " the Lingti valley, one of the tributaries of the Tsdrap 
valley " appear to correspond so closely in character with the Po series, 
that they are possibly merely its northern continuation. Further to the 
» Memoirs:, G. S. I., vol. XXII. p. 171. 
( 57 ) 
