32 



SECOND YAUKAND MISSION. 



into regular limestone conglomerate. Above 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 -building corals, crinoid stems, and a large Spirifer, the 

 sections of which, when seen on the surface, have a striking resemblance to those of Hegalodon. 



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, Productus sentireticulatus, and an 

 Atliyris. 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 this part of the hills consists in the occurrence of extensive plains 

 to wliich 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 wliich 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. 



