CATS 
indicate the superficial end of the skeleton-columns. They are 
however smaller than O. neodispansa: d1*/,—3, 4 = 1—1'/, mm. 
Horizontal section. The embryonal chamber is large and has thick 
parietes (d max. 270, thickness of the parietes 20 u). The chambers 
round it are half-circular, and further towards the periphery pretty 
well rounded hexagonal, but always irregular. It is very typical 
that the median chambers at the periphery are not placed in con- 
centric circles, but in the circumference of concentric hexagons, the 
sides of which are somewhat concave to the outside. Horizontal pori 
between the median chambers are not visible, but very many verti- 
cal pori can be observed. The lateral chambers are irregularly 
limited and have a wide lumen. They are united together by many 
almost horizontal pori. The diameter of the median chambers is 
45 —50 u; the thickness of the parietes 15 u. 
Too little is known of the interior structure of O. neodispansa to 
enable us to decide whether the described form agrees in every 
respect with this sort; the resemblance in outward characteristics 
however is so great that I have not hesitated to describe these Le- 
pidocyclines of the Sungei Mentawir as a variety of O. neodispansa. 
O. (Lepidocyclina) glabran sp. 
Ultimately about 15 specimens of a somewhat larger Lepidocy- 
clina were collected at this place, characterized by the indistinctness 
or even the absence of superficial warts. By its form it has the 
greatest resemblance to O. neodispansa (d 2-5, h 1-2 mm.), but the 
absence of warts forbids us to class it with this form 
Horizontal section. Likewise by its micros- 
copic structure this sort is obviously separated 
from those hitherto deseribed. Most likely 
the embryonal chamber is large, the first 
peripherie median chambers are irregularly 
roundish ; towards the outside however the 
chambcrs become soon spatulate and show 
a peculiar typical central lamella which has 
the same shape as that of O. flexuosa, but 
is much thicker (fig. +). Perhaps there are 
in this primary lamella very fine channels. 
Rad. diam. of the median chambers 45, tang. 35 u. 
Lepidosemicyclina polymorpha n. sp. 
In the younger strata of the Sungei Mentawir we meet with a form 
75 
Proceedings Royal Acad. Amsterdam. Vol. XIII. 
