( 1131 ) 
median chambers are flattened in a radial direction (rad. diam. 17, 
tang. diam. 30 u). In these chambers already the parietes are thick 
(10 w); only an indistinct central lamella can be observed in the 
parietes. 
Towards the periphery the chambers become first hexagonal 
afterwards spatulate ; in these peripheral chambers the cavity of the 
ventricle however always remains oval. It is very typical that with 
this form, the chambers are placed so irregularly, so that very often 
not continued curves are linked between the concentric circles. The 
dimensions of the peripheral chambers vary considerably ; radial 
65—90 u tang. diam. 55 u. The number of concentric rings of 
chambers is more than 50 and less than 100. At some places of the 
preparations the more delicate structure of the parietes could be 
studied. Here likewise a central lamella can be distinguished which 
is however often indistinct. The secondary parietes are here sepa- 
rated much sharper from the later chamber-filling than with O. for- 
mosa, which however may partly be a consequence of the conservation. 
Here namely every chamber is filled with single crystal of calcite, whilst 
by O. formosa the ventricles were usually filled with an aggregate 
of exceedingly fine crystals of calcite. At some places the wide pori 
can be seen that lead from one median ventricle obliquely outward 
to two median chambers of the ring lying more peripherally. 
Numerous pori run from the median chambers vertically or some- 
what obliquely upward and downward to the adjacent lateral chambers. 
In the main the shape of the central 
chambers is the same as with O. formosa; 
the radial parts however are continued 
here as far as the periphery (fig. 2). 
Vertical section. In the vertical section 
one sees very distinctly the increase of 
the vertical diameter; the strong, central 
skeleton-column is especially on one side 
clearly represented. The system of the 
median chambers consists of only one 
Fig. 2. stratum, the chambers are low (45 u) and 
their horizontal parietes are very thick (25 w. The pori between 
the median and the lateral chambers are represented here lengthwise ; 
it appears likewise that the lateral chambers communicate with each 
other by means of many wide, vertical pori, which are partly infil- 
tered with a brown mineral containing Fe. The number of strata 
of lateral chambers on both sides of the median plane amounts to 
about 20. 
