(MBR) 
of Lepidosemieyliua, corresponding in structure entirely to the older 
form of the Sungei Blakin, so that we can refer to the latter. Exter- 
nally the young form differs greatly from the primitive form, espe- 
cially by its great variability. Some forms are found that can hardly 
been distinguished from L. thecideaeformis, other specimens are 
strongly plaited, scalloped at the peripherical edge, are considerably 
protracted in a radial direction and have even a quite irregular shape. 
There are some features that point very vaguely to the fact that 
thecideaeformis was able to creep, whilst L. polymorpha had become 
fastened. Whilst namely the other Orbitoids are constructed radially, 
which with great probability points to a floating way of living 
(plankton) L. thecideaeformis has not only become bilaterally sym- 
metric in a vertical direction, but has also obtained an upper- and a 
lower-edge (difference in convexity) and has consequently adopted the 
symmetry we are accustomed to find in creeping animals. Hereto 
comes however that the younger form shows so great a variability 
and such irregular forms as we are only accustomed to see of animals 
that are fastened (Ostrea). 
Besides the Orbitoids described we find in the marl of the Men- 
tawir still Amphistegina. 
In a few words we shall still discuss rocks of other finding- 
places containing only generically determinable fossils. 
As old as the clav-marl on the Sungei Pamaluan is a limestone, 
found on rather a large scale in the delta of the mentioned river. 
Herein the vertical section of a little Orbitoid, a Globigerina and 
perhaps also Amphistegina was found. The limestone is very compact, 
becomes scarcely transparent under the microscope and contains 
occasionally grains of pyrite. 
Younger than the Pamaluan-marl, but perhaps older than the Blakin- 
marl is a marly sandstone, found on the Sungei Binuwang. 
Under the microscope the marl appears to consist of polygonal 
grains of quartz united together by a cement rich in Fe- and Ca. 
It contains Amphistegina, a single Alveolina 5 mm. long, a few 
Orbitoides and a large spiral-shapedly constructed Formanifere (not 
Spiroclypus) entirely unknown to me. 
A marl that is found on the S. E. coast of Pulu Balang and of 
which a specimen contains a large enclosure of resin is entirely filled 
with Foraminifera, among which: Miliola, a very small Alveolina, 
Globigerina, Amphistegina, a small Orbitoid and others can be 
recognized. The marl contains many polygonal grains of quartz, 
whilst the fossils often enclose grains of pyrite. 
Consequently the Orbitoides deseribed above may be classed into 
