( 1134 ) 
\ 
whilst they are moreover placed very irregularly; it is difficult to 
find back here the concentrical rings. The parietes of the median 
chambers are always thick; there was no vestige of a primary 
central lamella. Very numerous pori run vertically or obliquely, even 
horizontally, from the median chambers to the lateral ones. 
Vertical section. There is but one stratum of median chambers, 
the height of the ventricles is 55 u, the thickness of the horizontal 
parietes 10u. It is very distinctly to be seen how the skeleton- 
columns begin only at some distance from the median plane, and 
become gradually thicker towards the periphery. On either side of 
the median chambers are only 11 strata of lateral chambers. 
QO. (Lepidocychina) sumatrensis Brady. 
This form is by far the most numerous at the Sungei Blakin. It 
can very easily be distinguished from all other forms of the same 
place; with O. sumatrensis, which has been minutely described 
especially by Nrwron and Horranp (Le.) it shows only slight 
differences, which are not sufficient to make a new species of it. 
The disk has never or scarcely ever warts at the surface, it is 
very thick (d2—4,h2—2,7 mm.) and sometimes even cylindric. 
In the middle, one can follow a thin wedge often ending in flaps. 
Horizontal section. This form is megalospheric; the embryonal 
chamber is partly surrounded by the second chamber, just as with 
O polygona and the little Orbitoides of Timor described by Martin (L.c.). 
The outer-parietes of these two chambers is 33 u thick ; the separating 
parietes between the two chambers only 10. The maximal diameter 
of the embryonal chamber, is 190 #7, that of the second chamber 
310 u. The median chambers are more rhombus-shaped than spatulate, 
situated in rather regular concentric rings, often lengthened in a 
tangential direction. Their diameter is tang. 90, rad. 60—70 u. The 
median lamella is indistinct. The number of concentric rings is 30—50. 
The shape of the lateral chambers is not so irregular as witb the 
greater part of Orbitoides; they are also placed in rather regularly 
concentric rings, which is likewise mentioned by Newton and 
Houuanp (l.c.) about O. sumatrensis. f 
Vertical section. There is only one stratum of median chambers 
and on either side of these 15 strata of lateral chambers. Though 
at the surface no warts can be observed, if appears that there exists 
doubtlessly in the interior a firm interjacent skeleton. The height of 
the lateral chambers is 70 u, the thickness of the horizontal parietes 
is 30 u. 
