16 PROCEEDINGS OF THE NATIONAL MUSEUM vol.67 



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

 mesopores, 0.06 mm.; diameter of zoariiim, 2.5 by 1.5 cm. 



Structure. — The zoarial base is an epitheca concentrically wrinkled 

 flat, or concave. Some zoaria completely surround small shells. 



Exteriorly there are no subcolonies visible, as in D'Orbigny's fig- 

 ure, so that our determination of the species, made according to zoa- 

 rial analogies, is doubtful. We know, however, that this character 

 disappears easily upon the least superficial alteration. 



In meridian section the tubes are cylindrical and the mesopores of 

 variable length. The tubes are annular and their walls vesicular. 

 The small parietal vesicles correspond to the successive annuli of the 

 tubes. The subcolonies are clearly outlined by their initial tubes. 



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

 Switzerland (rare). 



Plesioty pes. —Cat. No. 69856, U.S.N.M. 



MULTICRESCIS LAMELLOSA, new species 



Plate 21, figs. 7-9 



Description. — The zoarium is free, large, lamellose, orbicular, formed 

 of many thin superposed lamellae. The inferior face is wrinkled 

 concentrically. The apertures are polygonal, arranged in irregular 

 quincunx. The mesopores are smaller, polygonal, irregularly placed. 



Measurements. — Diameter of apertures, 0.12 mm. ; diameter of meso- 

 pores, 0.08 mm.; zoarial diameter, 2.5 cm. 



Structure. — -The specimen figured is the largest fragment observed ; 

 it belonged certainly to a large orbicular colony. 



In meridian section the tubes are cylindrical, short, recurved at 

 their extremity. The mesopores are rather short. The walls are 

 entire. 



Affinities. — In zoarial aspect this species much resembles that 

 which we have called Multicrescis landrioti Michelin, 1841, but differs 

 in its greater micrometric dimensions and in sections by the nonan- 

 nulated tubes. 



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

 Switzerland (rare). 



Cotypes. — Cat. No. 69857, U.S.N.M., and Museum Comparative 

 Zoology. 



MULTICRESCIS MAMMILLOSA, new species 



Plate 21, figs. 5, 6 



Description. — The zoarium encrusts shells and is formed of many 

 thin superposed lamellae. The orifices are polygonal or suborbicular, 

 arranged in quincunx. Tlie mesopores are few in number, polygonal, 

 smaller than the orifices, irregularly placed. The zoarial surface is 

 mammillose. 



Measurements. — Diameter of apertures, 0.10 mm.; diameter of 

 mesopores, 0.06 mm. 



