498 ^ L. Dudley Stcanp — 



{A. perimense of Noetling), crocodilian and chelonian remains. At this 

 lower horizon Mastodon and Hippopotamus seem to be rare or absent, no 

 undoubted occurrence being known to the writer. 



(b) A conglomeratic band some 4,500 feet higher in the series and exposed 

 along the banks of the Irrawaddy between Yenangyaung and Nyaunghla 

 yielding numerous Mastodon latidens, Stegodon clifti, and Hippopotarmis 

 irravaticus.^ 



The lower horizon, that is the base of the Irrawadian at 

 Yenangyaung, may be correlated with the Dhok Pathan horizon ^ 

 (Upper Pontian), or, since Mastodon and Hijjpopota^nus both seem 

 to be absent, possibly with the Nagri horizon (Lower Pontian) of 

 J^orth-Western India. ^ In any case, Aceratherium indicates a pre- 

 Pliocene age. The higher horizon agrees faunally with the Tantrot 

 horizon (Lower Pliocene) of ISTorth- Western India. The presence of 

 later Pliocene deposits amongst the Irrawadian is indicated by 

 the presence of Bosela2Jhus and Bos further north in latitude 22° 3' 

 (L. D. S.). 



The Irrawadian probably extended much further south than it 

 does at present. It may occur under the alluvial deposits of the 

 Irrawadi delta ; indeed, a fossil bed containing Irrawadian 

 vertebrates mingled with fish remains (Lamna), and probably in 

 situ, has been recorded from below the alluvium near Rangoon.* 



V. Some Tectonic Considerations. 



Whilst the buckling of the Tertiary geosyncline was going on 

 throughout the Tertiary period, the main folding has affected even 

 the highest Irrawadian, and is thus probably late Pliocene. It may 

 be noted that, as with the folding in Burma, the end of the 

 Cretaceous and the end of the Pliocene were two of the most 



^ Dr. G. E. Pilgrim, in his revision of the vertebrate fossils of the Irrawadian 

 of Burma {Eec. G.S.I., vol. xl, pt. iii, 1910, p. 196), has confused the specimens 

 from these two horizons. He gives them in one list and says " It seems 

 certain, however, that from the lowest beds [sic] of the Irrawadi series 

 both Noetling and Grimes collected a distmctive vertebrate fauna which 

 I have examined. ..." If, however, one consults Noetling's account 

 {Mem. G.S.I., vol. xxvii, pt. ii, 1897, especially pp. 57, 58, and 59) one finds 

 he says " specimens are particularly common along the river bank between 

 Yenangyoung and Nyouaghla. . . . " ; again, " I am absolutely sure that 

 certain species are restricted in the neighbourhood of Yenangyaung to the 

 lower parts of the division. . . ." ; then, after separating a lower " zone " 

 of Hippotherium antelopinum and Aceratherium perimense from a higher " zone " 

 of Mastodon latidens and Hippopotamus irravaticus he says that the two latter 

 almost certainly do not occur lower. Grimes (Mem. G.S.I., vol. xxviii, pt. i, 

 1900, pp. 30-79) separates the Irrawadian into four " zones " ; from the lowest 

 he only mentions Cervus sp., then after describing his highest " zone " as 

 being exposed along the banks of the Irrawaddy says " It was from conglomerate 

 beds of this zone that Mr. Crawfurd, Dr. Oldham, and in late years Dr. Noetling 

 have obtained numerous fossil vertebrate bones. . . ." (p. 64). The writer's 

 personal experience confirms these statements. 



2 PUgrim, Rec. G.S.I. , vol. xliii, pt. iv, 1913, pp. 264-326. 



* Or by direct comparison with France, an even earlier age is indicated. 



4 Pilgrim, Rec. G.S.I., vol. xxxiii, pt. ii, 1906, pp. 157-8. 



