74 



PROCEEDINGS OF THE NATIONAL MUSEUM 



Affinities. — This species differs from Diplocava incondita in its 

 larger zoarium, in the smaller measurements, and in the considerable 

 separation of the groups of large tubes. It differs from Diplocava 

 glohulosa in its arborescent zoarium and in the separation of the 

 gi'oups of larger tubes. 



The sections show the usual structure of Diplocava. They indi- 

 cate that the central colony may be covered over by an exterior 

 incrusting lamella. 



Occurrence. — Lower Creta- 

 c eo u s (Valangian) : Sainte- 

 Croix (Vaud), Switzerland 

 (very rare). 



Cotype.— Cat. No. 69927, 

 U.S.N.M. 



DIPLOCAVA GLOBULOSA, new species 



Plate 11, figs. 9-11 



Description. — The z o a r i - 

 um is a globular multilamel- 

 lar mass ; it is free or incrusts 

 shells (Semimvlticava) . The 

 large cells are grouped in or- 

 bicular spaces which are 

 somewhat convex. The 

 small zooecia form zones of 

 more or less width around 

 each group of large orifices. 

 Measurements. — Diameter 

 interior of large tubes, 0.16 

 mm.; diameter interior of 

 small tubes, 0.10 mm.; di- 

 ameter of zoarium, 10 mm. 

 Structure. — In secti o n i n g 

 the elliptical zoarium along 

 the large axis one would ex- 

 pect to cut the zooecia along 

 their length, but this does 

 not happen, as the section cuts only the expanded extremity of the 

 tubes. In this genus the direction of the tubes is absolutely inde- 

 pendent of the zoarial form and the direction can only be surmised 

 from the exterior. As may be readily observed , the large tubes occur 

 only in the convex portions, while the small tubes are limited to the 

 concave portions; the difference between them is of little importance. 

 In tangential section the tubes are rounded and included in the 

 thick hexagonal walls. The difference in size between the large and 



