204 
llETECAVA. 
'W'liich the apertures are restricted. The branches are usually 
free, but occasionally dissepiments may connect them. 
Zooecia opening in transverse vertical rows of from three to six. 
The peristomes are low. 
Epitheca on reverse surface marked by strong punctures, 
irregularly arranged. 
Disteibutiox. 
Maastrichtian — ]\Iaastrichter Kreide : ^laastriclit ; Geulbeira. 
Eiguee. 
Fig. 18. Transverse section across a branch, X 20 tlia. 
^laastrichter Kreide : ^Faastricht. Van Breda Coll. D. 4497. 
Fig. 18 . — Rctecava geometrica (Hag.). 
Affinities. 
This Bryozoan is veiy nearly allied to Crisidmonea lichenoides, 
from which the iDiincipal difference is that the epitheca appears 
reticular instead of marked by linear depressions. Von Hagenow’s 
figm’e suggests a striking difference in the aperiures, which, 
however, is due probably to the peristomes haring been worn down. 
The reticular, coarsely porous nature of the epitheca in this 
farm is of interest, as it marks an approach to the condition met 
with in Horn era. 
That the ‘ canaux de renforcement*’ of Pergens are of little 
account in this genus is clear from the structime of R. geometrica, 
as shown by the figure of a transverse section. The dorsal axis is 
shown to consist of a series of fine tubes, which, however, are only 
the proximal ends of the zooecia ; the epitheca is seen as a thin 
basal lamina covering the reverse side. The section passes on the 
left side along the series of apertures, but this part of the section is 
incomplete and only one peristome is shown in the figure. 
