32 
SECOND YAKKAND MISSION. 
into regular limestone conglomerate. Aboye this are beds of solid grey dolomitic limestone, 
partly massive, partly stratified; the former possessing the character of reef limestone, and 
portions of it are indeed full of reef-bnilding corals, crinoid stems, and a large Spirifer, the 
sections of which, when seen on the surface, have a striking resemblance to those of Megalodon. 
North of Tongitar and about Bash-sogon I met in several places great numbers of fossils, 
but they were so firmly cemented in a calcareous matrix that only a few could be extracted. 
Among these I could recognise a small Bellerophon, Broductus semireticulatus, and an 
Athyris. A new Terebratula was also very common. Here, about Bash-sogon and Tugha- 
mati, greenish shales occurred often interstratified with the limestones, beds of which were 
highly carbonaceous ; the shales appeared to be unfossiliferous. 
The limestone hills, which, as already stated, are a continuation of the Koktan range, 
extend in a north-easterly direction the whole way to south of the Belauti pass, where they 
are overlaid by a particularly well-bedded dark limestone very similar to that containing 
Megalodon north of Chung-terek. On this limestone rest greenish and purplish sandstones 
and shales which occupy the pass and the adjoining hills to the north-west of it; minera- 
logically these last rocks are quite identical with what we understand under the name of 
“ Bunter sandstein ” and it is by no means improbable that the Belauti beds are also of 
triassic age, as they succeed in regular layers those of the carboniferous formation. 
A peculiar feature in tills part of the hills consists in the occurrence of extensive plains 
to which the name jilga is generally applied. It means originally, I think, merely a water¬ 
course, and, on a large scale, these plains may be looked upon as water-courses of former 
water-sheets. They occur at the base of the high range, and in some respects resemble the 
duns of the southern slopes of the Himalayas. North of Tongitar one of these large 
plains occurs within the limestone rocks, being surrounded by them on all sides. It must 
be about 30 miles long from east to west, and about 16 from north to south. Several 
isolated limestone hills and ridges occur in it, and it is drained off by the Bogoz and Sogon 
rivers, the former rising in the south-west, the latter in the south-east corner. The average 
elevation is about 5,000 feet. The greater portion is covered with a low scrubby vegetation, 
and, near the rivers, with high grass. The principal camping grounds are Bash-sogon and 
Tughamati. The whole plain, which affords good pasturage ground, is occupied by about 
120 tents of Kirghiz during the summer. 
The next jilga is the Jigda Jilga. It differs considerably both in its physical situation 
and in its general character from the former. It stretches from west by south to east by 
north for about 35 miles, while the diameter of the eastern half is about 20 and that 
of the western about 12 miles. Save for a few low hillocks it is almost a level plain 
throughout. On the north-western, northern, and north-eastern side it is bounded by the 
Koktan range, from which several water-courses lead into it, one about the middle from the 
north, and one from north-east of considerable size, this containing a large quantity of 
crystalline pebbles ; the rock from which they are derived must be in situ near the axis of the 
ridge. A third big stream comes from the east, leading from the Uibulak pass. None of 
these streams had any water in them. On the south, east, and south-east the plain is bounded 
by the much lower hills composed of Artysh beds; their slopes covered with gravel. 
An elevated gap or saddle situated in the south-west corner appears to connect this jilga 
with that of Tughamati. There is no drainage from this jilga; all the water is absorbed by 
the enormous thickness of sand and mud which fills the entire basin. 
