AET. 21 CYCLOSTOMATOUS BRYOZOA CANU AND BASSLER 21 



They are vesiculose either totally or partially (at the extremity). 

 The vesicles are quite variable in form and in size. When large 

 they give to the walls a moniliform aspect, which reveals sometimes 

 annular tubes. When they are very small the tissue is dense and 

 the preparations are little transparent. Finally, if their distal and 

 proximal walls are thin, the zooecial walls seem then entirely hollow. 



The vesicles are very difficult to draw and it is only by photog- 

 raphy that they can be figured with fidelity. 



In the course of this study we have not paid enough attention to 

 the structure of the zooecial walls not only of the Ceriopores but also 

 of many other species described, for in searching for the general laws 

 we have neglected the details. We can affirm that very close study 

 is always necessary because we are convinced that the microscopic 

 structure of the zooecial walls is the best specific character. Good 

 photographs with an enlargement of at least 50 diameters are also 

 necessary. 



Transverse sections. — The structure of the Ceriopores does not differ 

 from that of other cyclostomata, and we have found in transverse 

 sections the characters observed and described hitherto. We have 

 observed (1) polygonal zooecia with thin adjacent walls occurring 

 more often in the central part of the zoarium; (2) round, nonadjacent 

 zooecia, corresponding to the tubes with vesicular walls and with 

 their separation depending upon the thickness of their walls; (3) 

 polygonal zooecia in which the interior is rounded, corresponding to 

 the tubes with walls having many longitudinal rows of vesicles; and 

 (4) tubular zooecia which correspond to the recurved parts of the 

 tubes and are always vesicular. 



CERIOPORA TENUIS, new species 



Plate 22, figs. 12-14 



Description. — The zoarium is very thin and encrusts shells. The 

 orifices are polygonal and regular, with walls little thickened. 



Measurements. — Diameter of aperatures, 0.10 mm. Only the fig- 

 ured specimen has been found. 



Occurrence. — Lower Cretaceous (Valangian) : Sainte-Croix (Vaud), 

 Switzerland. 



Holotype— Cat. No. 69862, U.S.N.M. 



CERIOPORA OVOIDEA, new species 



Plate 22, figs. 2-5 



Description. — The zoarium is free ovoid, pedunculate, borne on a 

 very small flat base, formed sometimes of lamellae entirely covering 

 the base. The apertures are polygonal and irregular. The zonal 

 lines become transformed in basal lamellae. 



