ANCIENT MAN IN AFRICA AND JAVA 259 
the fossiliferous stratum must be assigned to a late part 
of the Pliocene period. The section of the Trinil 
strata reproduced in fig. 89 is therefore comparable to 
that of the Cromer forest beds given in fig. 74, p. 212. 
Below the fossiliferous bed is a stratum of conglomerate, 
representing the gravel bed of the ancient Bengawan. 
Under the conglomerate is a layer of clay — a deposit laid 
down in quiet, muddy water. Under the clay rests a 
marine deposit containing fossil shells of early Pliocene 
forms — corresponding to the "Crag" formations of 
East Anglia. Over the fossiliferous bed in which the 
remains of Pithecanthropus were found are stratified 
deposits amounting to 45 feet in thickness. These 
stratified beds of sand and fine, volcanic debris recall 
the Mauer sands overlying the Heidelberg mandible. 
Both at Trinil and Mauer the strata represent valley 
deposits. The fossiliferous bed, made up of a fine, 
triturated deposit of volcanic ashes and sand, represents 
the basal layer. After the valley deposits had been laid 
down during a period of subsidence, elevation of the 
land commenced, the stream then cutting a new valley 
out of its old deposits and exposing the deeper strata on 
its banks. Dr Dubois, who was a surgeon in the 
colonial military service of Java at the date of this 
discovery, and who is now Professor of Geology in the 
University of Amsterdam, came to the conclusion that 
the animal remains in the fossiliferous layer belong to a 
late phase of the Pliocene period — one corresponding 
to the forest beds of East Anglia. The remains of 
Pithecanthropus, which were discovered in that stratum, 
would thus belong to a somewhat earlier date than the 
Heidelberg mandible. 
To settle the date more definitely, and in the hope 
of finding further remains of this fossil humanoid form, 
Frau Lenore Selenka, with assistance from certain 
scientific societies in Germany, fitted out an expedition 
in 1906 to continue Dr Dubois' exploration at Trinil.' 
' Die Pithecanthropus Schichtett aiif Java^ M. Lenore Selenka and 
Professor Max. Blanckenhorn, Berlin, 191 1. 
