Page:Provincial geographies of India (Volume 4).djvu/69

CH. VII] Ordovician exposures. It is found that this fauna resembles much more closely the Ordovician fauna of North Europe, especially of the Baltic provinces, than it does that of the central Himalaya. The Ordovician of the Himalaya in Spiti and Kumaon contains no cystids and extremely few trilobites, and its fauna generally resembles that of the American beds of the same age. We are constrained, therefore, to make the interesting deduction that in Ordovician times the Arctic sea which covered what is now Northern Europe, extended into Burma as far south as latitude 21° N., and was separated from the sea which covered the central Himalaya. The former sea spread over central and north-eastern China, but of its southern limit we know nothing as yet.

Lying upon the Ordovician are shales, sandstones and limestones of no less interest and importance. These beds, from the character of their rich fauna, belong to a system known as the Silurian, after an area in South Wales in which they were first studied. As in the Ordovician, trilobites and brachiopods are common, but the occurrence of most interest is that of the peculiar rod-like colonies of animals known as graptolites; these were found for the first time in Asia by Mr T. D. La Touche in December, 1899. The discrepancy between the Burmese fauna and that of the central Himalaya and America, noted in the case of the preceding system, is still more strongly marked in the Silurian. About 87 per cent, of the Burmese forms are identical with or allied to European forms, while only 35 per cent, are so related to America; only seven forms are common to Burma and the central Himalaya, and these are all ubiquitous forms. The Himalayan forms are allied to American and European in practically equal proportions. The central Himalayan fauna includes no graptolites and is predominated by corals, most of which have marked American affinities, while the Burmese fauna is characterized by abundant graptolites, several of which are