SILURIAN SYSTEM : NAMHSIM STAGE. 



161 



When we compare this fauna with the Silurian fauna of Spiti 

 ! and the Central Himalaya, as described, by 



ma ayan equiva en s. ^ Cowper Reed in a recent Memoir, 1 the 



same almost absolute want of concordance becomes manifest as in 

 the case of the Ordovician fauna ; while the discrepancy existing in the 

 relations of the species with those of America and Europe respectively 

 is still more strongly marked than in the case of the older strata. While 

 the 35 species described by Mr. Cowper Reed from the Silurian of the 

 Central Himalaya are allied with those of America and Europe in 

 practically equal proportions, 18 (51 per cent.) being common to 

 the former province and 17 (49 per cent.) to the latter ; out of 

 the 40 species described from Burma by the same author no less 

 than 35 (87*5 per cent.) are identical with or allied to European 

 forms, and only 14 (35 per cent.) to American. Seven only are 

 common to the Himalaya and Burma, all of these being ubiquitous 

 species like Orthis elegantula, O. calligramma, 0. rustica, Leptama 

 rhomboidalis, and Pentamerus oblongus ; while only one of the species 

 peculiar to Burma, Encrinurus konghsaensis, is represented by an 

 allied species in the Himalaya, E. punctatus, also a widely ranging 

 fossil. 



The contrast in the composition of the Burmese and Himalayan 

 Silurian faunas is also quite as striking as in the 



Composition of the . , .. , . . m , . 



f auna . case ot the Ordovician. 1 he presence of grapto- 



lites is in itself sufficient to show that there could 

 have been no direct communication between the two areas in Silurian 

 times ; for the character of the rocks of that age described by 

 Mr. Hayden in Spiti (Op. cit., p. 24) would not lead one to suppose that 

 the conditions were not suitable for the growth and preservation of 

 these organisms, if they had penetrated to that area. Again, the 

 distinctive characteristic of Hayden 's horizon 6, at the base of the Silu- 

 rian in Spiti, is the preponderance of corals, no less than 13 species having 

 been obtained from this horizon alone, of which 10 possess marked 

 American affinities. In Burma, on the other hand, Lindstrcemia 

 is the only Silurian coral yet found. In the higher horizons of Spiti 

 there is a more varied assemblage of fossils, but even among the 

 brachiopoda there is no close or peculiar connection with those of 

 Burma, only the most widely ranging forms being represented in 



1 The Ordovician and Silurian Fossils of the (Vulval Himalaya. I'<il ,■ mi. hid., Vol. 

 VII, Mom. No. 2; a/sv. H. H. Hayden, The Geology of Spiti. with parts of I'.ashahr and 

 Rupshu, Memoirs, Ocol. Surv. Ind., Vol. XXXVI. Pt. 1. 



M 



