SILURIAN SYSTEM ZE13INGYI STAGE. 



179 



Bohemian or Heicynian facies. Among all the fossils described 

 from the lower groups there are only two that are of a distinct- 

 ively Bohemian type, viz., Aristocystis in the Ordovician and Mi- 

 mulus in the Silurian ; but in the Zebingyi beds we have, of 20 

 species described, 12 belonging to or closely allied with forms 

 from Bohemia or the ' Heicynkalke ' of the Harz ; while of these 

 6 are peculiar to that province, including such distinctive forms 

 as Lunulicardium amabile, Dualina (?) sp., Vlasta (?) sp., and Tentacu- 

 lites elegans. The only characteristic Northern or "Western Euro- 

 pean forms are Monograptus riccartonensis, Atrypa marginalis, a 

 widely ranging species, Tentaculites ornatus, and the cephalopcds 

 Orthoceras afF. mocktreense and 0. nicholianum, the identification of 

 both of which is doubtful. Some considerable change in the distri- 

 bution of land and sea must therefore have taken place in the 

 interval between the deposition of the Namhsim series and that 

 of the Zebingyi beds, but our information is as 3 et too scanty to 

 enable us to do more than speculate regarding the nature of this 

 change. 



Mr. Cowper Reed has discussed the question of the correlation 



of this fauna in his Memoir (Op. cit., pp. 152-154). 

 Migration of fauna. . Tr . e . 



and points out that a Hercynian fauna has 



been described by Tschernyschew from the western slopes of the 



Urals. He remarks that — 



'* Freeh has suggested that the birth-place of this fauna was situated 

 in the east and south-east of Europe and that its migration proceeded in a 

 westerly direction, so that it did not reach America till later Devonian times. 

 It is open to us now to speculate whether the heralds of this fauna did 

 not first appear in South-Eastern x\sia before the Silurian period came to an 

 end, and that thence* it spread westwards into Europe." 



But the Burmese evidence seems to nie to point rather the other 

 way, for we have a characteristic Wenlock graptolite, Monograptus 

 riccartonensis , associated with and on the same slab of rock as the 

 Devonian Tentaculites elegans ; and a glance at the list will show 

 that most of the other species are of Wenlock age in Europe, 

 while some are even older. 



As 1 pointed out in a note published at the end of Mr. Heed's 

 Memoir (page 154), there is no question of 

 No inversion of strata, an inversion of the beds, such as he suggests 

 might account for the presence of limestones 

 with a Hercynian fauna below tb.s graptolite shales The occurronce 



n 2 



