116 
Records of the Geoloyical Survey of India. 
[vOL. Xf, 
that no relations to forms in higher beds have been omitted, and that the evidence 
is in no case one-sided, all I can say is that Dr. Deistmantel’s ideas upon palseon- 
tological evidence differ widely from what I have always supposed to be the ac¬ 
cepted views of geologists in general. I may be in error, but I should have 
thought that in upper Jurassic strata some species would certainly be found 
closely allied to middle and lower j urassic forms, and that a few might be identical. 
I notice that all the species mentioned except the Plesiosaurus consist of Lamel- 
libranchiate bivalves {Pelecypoda'), and that Dr. Waagen, whose opinion on the 
subject is probably not given witliout reason, has especially referred^ to alliances 
between some of the Dmia Pelecypoda and those of the Portland beds, and 
I have always been under the impression that the selection of a few forms 
from amongst a large number as evidence of the affinities of a fauna is liable to 
mislead, and that the true relations are only to be determined by a comparison of 
the whole. Prom the Portland group itself, there would, I think, be no difficulty 
in selecting half a dozen species of mollusca allied to middle or lower Jurassic forms. 
Perhaps the value of the evidence adduced, assuming it to be correct, may be 
best shown by taking a parallel case. 
The cretaceous beds of Southern India comprise a group representative of the 
upper cretaceous rocks (white chalk with flints or Senonian) in Europe. In this 
Southern Indian group, that of Arialur, amongst other fossils, the following occur®— 
Nautilus Bouchardianus, founcl in Europe in the gault (middle cretaceous), 
N. Clemeniiims „ „ gault. 
Ammonites Velledee „ „ ncocomian and middle cretaceous, 
A. Deccanensis belonging to the group of macroeephali and allied to European 
A. Arrialoorensis j Jurassic forms, . 
Fulguraria elongata (Valuta elongata, D’Orb.) found in European middle cretaceous beds, 
Cerithium trimonile „ gault, 
Fuspira roUindata (Turho rotundatus, Sow.) „ upper greensand, 
ZizipMaus Geiniizams „ Hippuritio limestone 
(Tmonian), 
besides Ammonites Gardeni and Euiilirysalis gigantea, found also in South African 
beds supposed to be of Cenomanian (upper greensand) age. These identifications, 
be it recollected, with the exception of the two macroeephali ammonites, are speci- 
fie ; they are not mere cases of related forms, as in the fauna of the Umia beds, 
and the list might be considerably increased if evei-y form allied to European 
middle or lower cretaceous species were quoted. Tet there caimot be the slight¬ 
est doubt that the fauna of the Arialur beds is typically upper cretaceous, taken 
as a whole. It is, I think, needless to adduce further evidence to show of how 
little value the argument against the upper Jurassic age of the Umia beds would 
be, even if it were correct. 
But then comes the question—How far is this evidence correct? Three of the 
six mollusca mentioned are Trigonim allied to the South African forms Tr. vau, Tr. 
Herzogi, and Tr. ventricosa, and Dr. Peistmantel, quite correctly I believe, points out* 
* 1. c., p. 225. 
Eec. G. S. I., Vol. IX, p. 116. 
