BAO W. S. DUN AND SIR EDGEWORTH DAVID. 
approximate age of these Malay Archipelago strata is 
known, as tested by Northern Hemisphere standards of 
geological chronology, such a determination will help con- 
siderably to the more accurate placing in geological time 
of the Lower Marine series of Kastern Australia. 
At the Irwin River Coal-field the Gastrioceras occurs in 
extraordinary numbers, the individual specimens almost 
touch one another, and form a bed of clayey limestone only 
about 6 inches in thickness. Stratigraphically therefore it 
isa remarkably useful horizon for field mapping. Already 
Dr. Woolnough has traced these beds in the field for a 
distance of over 20 miles. 
The largest specimen collected is fragmentary, but is 
portion of the last whorl 6°2 inches in width, 3°25 in depth 
and indicates a diameter of about 12°5 inches for the com- 
plete individual. 
While some considerable time may be needed in order to 
elaborate the taxonomy of these forms (obviously a very 
important work as geological classification depends so 
much on higher forms like the Cephalopods) we think it of 
importance at once to place on record the fact of the great 
similarity, if not the absolute identity of Gastrioceras 
Jacksoni, Etheridge, from the Irwin River Coal-field, and 
Paralegoceras sundaicum, Haniel, from the Island of Letti.* 
For comparison of these forms we publish two suture lines, 
(figs. 2, 3), of Gastrioceras Jacksoni, and (fig. 1) the repro- 

Fig. 1. Suture line of Paralegoceras sundaicum, Haniel, op. cit., 
p. 164. 
t Jaar. van het Mijn. in Nederland Oost-Indie, 1914, Part 1, pp. 163 - 
165, pl. xvii. 


