68 PEOCEEDINGS OF THE NATIONAL. MUSEUM vol.67 



Measurements. — Diameter of interior orifice, 0.16 by 0.20 mm.; 



diameter of exterior orifice, 0.22 mm.; diameter of branches, 2.5 mm. 



Structure. — The basal parts of the zoarium have the Semicava 



growth of D'Orbigny, but the branches which they emit are sohd 



and their sections are identical with those of 



Ceriocava. 



It is difficult to predict the direction of the 

 tubes in an incrustmg colony in order to section 

 it correctly. 



In tangential section it may be noted that 

 Fig. Z4.~ceriocavajunctata, the tubes are polygoual, adjacent, but their in- 

 new species. Transverse terior is calcified and thus forms a rounded 



section, X16, througha. . 



solid cylindrical branch. mteriOP tubc. 



Lower Cretaceous (Vaian- Occurrence.— Ijowev Cretaccous (Valangian): 



gian): Sainte-Croix, Swit- ~ . /-i • /tt ix o • i i is / 



zeriand bamte-doix (Vaud), Switzerland (rare). 



Coty pes. —Cat. No. 69921, U.S.N.M. 



CERIOCAVA MULTILAMELLOSA, new species 



Plate 9, figs. 1-10 



Description. — The zoarium is free, cylindrical, dichotomous, formed 

 of many enveloping lamellae; the outermost lamellae are incomplete 

 and show at their extremity a short zone of growth. The facettes 

 are hexagonal, arranged in transverse rows, perforated at the center 

 by the aperture. The aperture is orbicular and surrounded by a 

 thin and somewhat salient peristome. The orifices of the tubes 

 without facettes are irregularly polygonal. 



Measurements. — Diameter of apertures, 0.08 mm.; diameter of 

 peristomes, 0.10 mm.; diameter of facettes, 0.16 mm.; diameter of 

 larger branches, 2.5 mm. 



Structure. — The extremity of the branches is conical, as in all 

 colonies in which the tubes are expandetl. This conical part is con- 

 sidered as the zone of growth and the orifices here do not bear 

 facettes (fig. 3). 



The exterior lamellae grow around the interior trunk and appear 

 around it as a rather thick but short zone of growth (fig. 2) ; these 

 lamellae bear facettes like the central trunk. 



The facettes are often well distributed over all the colony (figs. 

 2, 3), but frequently they appear only in zones (fig. 5). We can not 

 affirm that their existence is normal, for entire branches are deprived 

 of them and seem even never to have had them (fig. 9). The appear- 

 ance of facettes in the genus Ceriocava still remains a mystery. Per- 

 haps they are very fragile, as in Meliceritites , and disappear easily by 

 slight abrasion. 



