( 1128 ) 
as the other chambers reach to the immediate vicinity of the centrum. 
Most of the central chambers that are next to the embryonal one 
are flattened in a radial direction, the radial diameter is 40—60, the 
tangential one 60 —80 u. Only farther towards the periphery the 
median chambers become pretty regularly six-angular, whilst the 
most peripheric ones are spatulate. In general the size of the chambers 
increases towards the periphery, but occasionally rings of smaller 
chambers occur between larger ones. Whilst by far the greater part 
of the median chambers are ranged in circles, their arrangement 
in the centrum is a little more irregular, and at the periphery 
sometimes not continued curves are linked between the continued 
concentric circles. The number of concentric circles of median 
chambers amounts fo more than 100. The radial diameter of the 
peripheric chambers is 150—250 u, their tangential diameter 140— 
150 w. Especially at the periphery the parietes of the median chambers 
show a typical structure (fig. 1). The 
parietes namely consist of a dark 
untransparent central lamella to which 
granular, grey calcite sticks. In this 
section the central lamella is not 
continued round the chambers, but 
consists of a tangential, peripherial 
curve, two tangential, central parts 
of a curve (each the half of a tangen- 
tial peripherial curve of chambers 
placed more towards the centrum) 
and of two radial lamellae, ending 
towards the centre in a tangential 
curve. Perhaps there is above this 
little curve a porus of a tangential shape uniting the chambers of 
the same curve. In many ventricles the central lamella is on all 
sides covered by symmetrically thick secondary parietes, in others 
these secondary parietes are thinnest on the tangential parietes. 
Vertical section. From this section appears likewise that the 
embryonal chamber must be very small, though it is not visible 
itself. The height of the median chambers namely decreases from 
the periphery to very close to the centre from 120 to 60 u. The 
peripherical parietes of the median chambers are always convex to 
the outside, the structure of the parietes is only very unsatisfactorily 
visible. The lateral chambers have very thick parietes, and are 
strongly flattened in a vertical direction; their height is 30—50 u 
the thickness of the parietes 30—40 w. Because the parietes are 
