THE LARGER FAUNAL HORIZONS. 49 
THE LARGER FAUNAL HORIZONS. 
The geographic distribution and characters of the Lower, Middle, and 
Upper Cambrian divisions of the eastern and southern Asiatic Cambrian 
faunas vary to such an extent as to make it desirable to consider them 
separately. It seems from our present information that the Cambrian sea 
first transgressed the southern and southeastern sections of the continent in 
late Lower Cambrian time and that certain changes occurred in its distribu- 
tion at intervals during the remainder of Cambrian time. The data, however, 
are still too limited to give more than very approximate limits to the distri- 
bution of the faunas. Extended areal mapping of the distribution of the 
geologic formations and faunas will be necessary before paleographic maps 
of eastern Asia can be made that are more than broad outlines to be changed 
and filled in very much as the geographic map of Africa was modified from 
time to time during the last half of the nineteenth century. 
Lower Cambrian Fauna.—The Lower Cambrian (Man-t’o shale) Redlichia 
fauna of Shan-tung, Shan-si, Yun-nan, and northern India is, so far as known, 
very distinctive and confined to the Asiatic continent and Australia. 
The fauna is unknown in Manchuria, although Blackwelder considered 
that the Yung-ning sandstone of southern Liau-tung was probably of Lower 
Cambrian age. [Blackwelder, 1907, p. 87.] 
In this and the following lists I have combined the local lists, placing 
after each species the locality number, so that each species may be traced back 
to its local list and thus found with its immediate associates in the strata. 
In Central Shan-tung the Man-t’o sandstones contain a small fauna, as 
follows: 
Billingsella richthofeni (C3, C20) Redlichia sp. undt. (C6) 
Obolella asiatica (C17, C32’) Ptychoparia aclis (C17, C20, C31) 
Helcionella rugosa chinensis (C3) Ptychoparia granosa (C17) 
Hyolithes delia (C3) Ptychoparia impar (C17) 
Hyolithes sp. undt. (C 32’) Ptychoparia ligea (C31) 
Redlichia chinensis (C15, C16, C27) Ptychoparia (Emmrichella) constricta (C3) 
Redlichia nobilis (C3) Ptychoparia (Emmrichella) mantoensis (C20, C31) 
Of the above, Obolella asiatica, Helcionella rugosa chinensis,and Redlichia 
chinensis may be considered as characteristically Lower Cambrian. I do 
not know of the occurrence of the genus Obolella above the Lower Cambrian 
[Walcott, 1912, p. 588], and Helcionella rugosa belongs to the same fauna. 
Redlichia chinensis and R. nobilis have been referred to as descendent from 
Olenellus [Walcott, 1910a, p. 254], but I would now cite Callavia in place of 
Olenellus, as the latter genus appears to have left no descendants. It should 
also be noted that the very ancient form Nevadia has a tapering glabella and 
long eye-lobes [Walcott, 1910, plate 23], which leads me to consider Redlichia 
as an example of reversion toa more primitive type in the form of the glabella. 
The thorax and pygidium of Redlichia are more like the same parts in Wannerta 
[Walcott, 1910a, plate 30], except for the median spines of the thoracic 
segments. 
