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The sphæronites of the Mashabroom are probably a new species; they were found in considerable variety, from the size of a small walnut to that of a large orange; the largest were perfectly round and polished like a cricket ball, without warts, spines or facettes, pierced by numerous pores. Some of the smaller have the stems scarcely visible (fig. 6, Pl. VIII), and are covered either with large tracts set well apart or with smaller ones set closer; some spines are depressed or lenticular; all are pierced by innumerable pores, none shows traces of polygonal plates; mouth not to be seen in any of the specimens I have examined. (See figs. 5, and 6, pl. VIII and plate IX fig. 1.) The discoverer, not being a geologist, did not look for other fossils: the cystidea were so numerous and so curious in appearance, that they gave quite a peculiar aspect to the ground.

The Mashabroom is stratified to its very summit, the beds being limestone and shales, dipping towards the S., at a moderate angle. This stratification is so well marked, that it can be distinctly noticed from a long way off. These sedimentary beds repose on metamorphic layers of mica-schist and gneiss. The limestone is extremely rich in magnesia, principally towards the base of the bed, where it passes into Steatite in patches (Austen). Some of the Serpentine and Jade (compact Tremolite) brought to Srinuggur and there worked into ornamental articles by the stone-cutters of that city, come, I believe, from the neighbourhood of the Mustak Range and of Mashabroom, though the greater quantity is supposed to be derived from the Yarkandkass valley and the Kuen-Luen Chain in Khotan. There can be little doubt that the limestone of the Mashabroom is the parent bed of the cystides found in the valley between two of the spurs of that mountain; and at least a portion of the limestone of Mashabroom is Silurian,

The following sketch-section embodies the information kindly given me by Mr. Ryall and Captain G. Austen.

1867.]

the Western Himalaya and Afghan Mountains.

2

OLACIER BACTORO

Approximate vertical Section of the Masha Brum mountain, one of the great summits of the Korakoram Chain, from S. to N. bearing W.

49

1, granite; 2, gneiss and micaschist; 3, sandy shales and coarse slate without fossils; 4, pale dolomitic limestone containing patches of Steatite; 5, pale ochre-coloured limestone, the probable parent rock of the Sphæronites found at the foot of the mountain.

To the north of the great glacier Baltoro is that portion of the Korakoram Range known as the Mustakh and crossed by the Mustakh Pass at an elevation of 18,400 feet. The whole S. Western face of this Mustakh is covered by enormous glaciers through which the rocky spurs of the mountains rise like islands and promontories. These rocks Captain Godwin-Austen found to be limestone dipping to the N. E., but he failed to find fossils in it, though he noticed traces and fragments of organisms. It is so very probable that these beds are a continuation of the limestone of the Masha Brum, that I have not hesitated to colour them in the map as Silurian. Of course, this requires confirmation. Unfortunately the difficulties of reaching even the foot of these gigantic mountains are nearly insurmountable.

80. I could not get any information on the nature of the rocks forming the remainder of the Korakoram Chain. The few European travellers who ever saw the chain, agree, I believe, in representing it as being mostly composed of granite.

On the other side of the chain we find, between it and the next parallel, viz. the Kuen-Luen Chain, the valley of the Yarkandkash (river), which extends from the Korakoram or Yarkand pass to Tashgurkhan, and the Akzai Chin or White Desert, which is continued towards the S. E., nobody knows how far. The valley of the Yarkand river and the Akzai Chin are separated one from the other by a low ridge of mountains similar to the masses of mountains found between the other great chains of the Himalaya. All we know of the valley of the Yarkandkash is that some mines of rock-salt occur there, and that both in the beds of the Yarkandkash and Karakash and in the the ravines of the neighbourhood, some pebbles are collected and used for cheap jewellery; and these pebbles are either quartzy stones or rocks decidedly volcanic. There is apparently some analogy between these mountains and those of the centre of Rupshu and of Ladak. The Akzai plain is also very similar to the countries just mentioned, in at least the one character of being an elevated, rainless desert, spotted with small lakes, some fresh, and others salt.

It is superfluous to say that I know nothing of the Geology of the Yarkandkash and Karakash valleys and of the Aksai Chin; neither is there anything known of the formation of the Kuen Luen or Piryukh Chain, except that it is reported to contain valuable copper and gold mines. Another small chain or range, half way between the Kuen Luen and Yarkand seems to be the last parallel of the Himalaya. Yarkand is supposed to be in latitude N. 38° and about 5000 feet above the sea. From the top of the Korakoram pass to the foot of the hills, the distance is approximately 110 miles, and the descent 13,000 feet or about 118 feet per mile, a mild slope for a mountainous country.

(To be continued.)

Contributions to Indian Malacology, No. VIII. List of Estuary shells collected in the delta of the IRAWADY, in PEGU, with descriptions of the new species. By WILLIAM T. BLANFORD, A. R. S. M., F. G. S., Cor. Mem. Z. S. &c.

[Received 14th November, 1866.]

A short visit to Calcutta, and access to various works on conchology which have, for some years past, been beyond my reach, have enabled me to prepare the following list of the species of mollusca collected by me in the Pegu delta during the early portion of 1862. In March and April of that year, whilst engaged in the Geological Survey of the country south of Bassein, I was compelled to traverse the net. work of creeks which intersect the Irawaddy delta in every direction, and, in so doing, I had many opportunities of searching for the various mollusca inhabiting the channels of brackish and salt water.

The western portion of the Irawady delta south of Bassein is of peculiar character. Instead of the endless alluvial flat which is usually alone met with near the mouth of large rivers, the country is frequently undulating, and even, in places, hilly; the hills being surrounded by plains of alluvial soil intersected by tidal channels. Rock not unfrequently occurs in these creeks, and affords a habitat for many mollusca which are not met with in the usual muddy flats.

The Bassein river itself, one of the numerous mouths of the Irawady, like the Mutlah and other great channels of the Ganges delta, is at present rather an arm of the sea than a river; as it receives no fresh water directly from the Irawady except during the height of the rains. In the cold weather the water is perfectly salt for many miles above the mouth, and marine animals abound. Thus for many days, during the time I was traversing the neighbourhood, the water swarmed with Medusæ. The volume of fresh water which pours into the Bassein river can at no time be very large, for the mollusca which inhabit the southern side of Negrais Island, some distance within the mouth of the river, are typically marine, comprising species of Parmophorus, Triforis, Trochus, Chama, &c., and not including any of the usual estuary forms Assiminia, Amphibola, Neritina, &c., whilst at Poorian Point and Pagoda Point, the two headlands which form

the entrance to the Bassein river, precisely the same mollusca occur as along the Arakan coast near Cape Negrais.* At the mouths of those channels by which the mass of fresh water poured down by the Irawady reaches the sea, I do not think that any typically marine animals are met with, nor could they exist, for, in the height of the rains, I have found the water outside the mouth of the Rangoon river perfectly fresh and drinkable, and yet this is only a minor channel compared to the Chinabuckeer and the neighbouring branches, down which the great bulk of the water pours.

To the greater saltness of the Bassein river I attribute the presence of the numerous marine types mentioned in the following list. It will be seen that a few distinctly marine species were met with; the number, however, was small. There are also in the list two or three genera, forms of which do not appear to have been hitherto found in estuaries, e. g. Tectura, Sphenia, Scalaria; whilst, on the other hand, the genus Scaphula had previously only been met with in fresh water.

The fauna and flora of the Irawady delta appear to be twofold.† Farther from the sea, where the water is more or less brackish, the creeks are mostly narrow and deep, with steep banks, which are covered at high water, and bordered by an unbroken belt of salt swamp, in which grow high trees, chiefly of Bruguieria gymnorhiza? The views along the creeks, with their borders of dense high forest, are often of great beauty. This belt of salt swamp and high trees varies much in breadth, from a few yards to half a mile or more; inside it are either open plains, which, if uncultivated, are covered with high grass, or else rises, usually of gravel, occasionally of rock, which are covered with jungle.

The mollusks of this tract comprise Neritina depressa, N. obtusa and N. Smithii; the species of Tectura, Modiola, Martesia and Sphenia named in the following list are met with wherever rocks occur; Scaphula is found under stones, Auricula and Cyrena inhabit the salt swamp. Teredo perforates the dead trees. Neritina cornucopia is principally met with in this region, but is also found lower down the

*Amongst others, I found species of Dolium, Ricinula, Ranella, &c.

I regret that my want of knowledge of botany and the paucity of the obser vations I was able to make upon the zoology, prevent me from entering fully into this subject. I can merely point out the fact that a distinction exists between the fauna and flora of the delta nearer to the coast, and that found further inlaud, and illustrate it in the single instance of the mollusca.

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