RH/ETIC STAGE. 



301 



few other fossils, and none that are specially characteristic of the 

 ' Avicula contorta ' zone. Further west, in 

 Northern Afghanistan, a series of sandy beds 

 with seams of coal was ascribed by Mr. C. L. Griesbach to the 

 Rhsetic, 1 but these beds have now been shown by Mr. Havden to 

 belong probably to a much higher horizon, and are considered by 

 him to be the equivalents of the plant-bearing beds of Russian 

 Turkestan, that is to say, deposited in a different basin from that 

 of the Triassic beds of the Himalaya. 2 No strata that can with 

 certainty be ascribed to the Rhsetic stage have yet been found in 

 that area. 



The composition of the Napeng fauna also presents a strong con- 

 trast to that of the faunas that preceded it, with 

 Composition of the the exception of the Wetwin shales, in that, so 



fauna. . . . . 



far as it has been described, it consists almost 

 entirely of lamellibranchs, with a few gastropods and a single 

 brachiopod. But it should be remembered that we know practically 

 nothing of the fauna that built up the limestones associated with the 

 shales, except that it must have consisted to a great extent of 

 brachiopoda and perhaps corals. Sections of the shells of brachiopods 

 and gastropods, and of the spines of echinoderms are not uncommon 

 in some of the limestones, and near Napeng I found the remains of 

 a 'large sea-urchin in a soft marly layer, but in such a rotten 

 condition that even the genus could not be made out. The similarity 

 in composition between the fauna of these shales and those of 

 Wetwin is significant, for it tends to confirm Mr. Cowpor Reed's 

 suggestion (see above, p. 254) that the peculiarity of the Wetwin 

 fauna is due to bionomical surroundings ; and indeed I have 

 very little doubt that the two sets of beds were deposited under 

 much the same conditions, repeated in the case of the Napeng shales 

 after a prolonged interval of time. The recurrence in the Napeng 

 beds of the American genus Palcroneilo, the most common fossil 

 represented at Wetwin, is very suggestive in this connection. 



The fossils collected from the ancient travertine deposit north 



,i„. fossils of Nawn Sl )in g ( Loc - 12 > D 3), mentioned on 

 p. 287, have also been described by Miss 

 Healey {op. cit., pp. 87, 88), but none of them can be definitely 



1 Field notes from Afghanistan ; Rrrorrls, < !<(>!. Sim: I ml., Vol. XIX, P(. t, p. 243. 



2 Geology of Northern Afghanistan ; M emoirs, Oeol. Surv. I ml., Vol. XXXIX pt 

 J, pp. 32, 79. 



