52 HAYDEN : GEOLOGY OF THE PROVINCES OF TSANG AND 0. 
dzong. A part of the southern side of the ridge is shown on PI. 12, 
fig. 2, on which (i) represents the ferruginous sandstone and (2) the 
massive limestone. The ferruginous sandstone is the lowest bed 
seen on the section, and to the east — right-hand side of the picture — 
it is almost entirely cut out by a fault, which brings the limestone 
down on to the upper Cretaceous beds (see also PI. 4). Between 
the sandstone outcrop and the base of the limestone cliff, most of the 
slope is covered with debris, but sandstone can be seen here and 
there at intervals for the greater part of the distance ; higher up it is 
replaced by thin-bedded limestone, which begins a short distance 
below the foot of the cliff. At the point marked x occurs the first 
fossiliferous horizon found above the sandstone; this is a narrow 
band of pale grey limestone full of foraminifera, which to the naked 
eye appear to be entirely Orhitolites sp. Under the microscope, 
however, the matrix is found to be largely made up of smaller fora- 
minifera, chiefly members of the family Miliolidas. At about twenty 
feet above this a section just to the east of that shown on PI. 12 
yielded a few badly preserved gastropods and a Nautilus. Above 
this scattered fossils occur throughout the limestone ; they are chiefly 
gastropods, with some echinoids and lamellibranchs, in almost all 
cases badly preserved internal casts v/ith no trace of shell. The 
total thickness of this limestone is difficult to estimate, owing to the 
universal faulting; both at Tiina and at Kampa dzong it appears 
to be about 300 feet, In the sections on the ridge immediately 
behind Kampa dzong, a band of shale, about 40 feet thick, occurs 
rather above the middle of the limestone ; it is not so conspicuous 
at Tiina, although a certain amount of shale is seen there also ; no 
fossils were found in it at either locality. 
The whole of this limestone series, which may be conveniently 
termed the "Gastropod limestone," appears to belong to one horizon. 
With the exception of the foraminifera, which are more conspicuous in 
the lower beds, the same fossils seem to occur throughout. Gastropods 
largely predominate and include several genera of which the com- 
monest are Ovula Cerithtum, Phasianella, Fusus, Valuta^ Conus 
( '73 ) 
