NORTH AMERICAN EARLY TERTIARY BRYOZOA. 379 



, "_ I /.s =0.48-0.50 mm. 



Measurements. Aperture) ' Zooecia 1 7.3=0.35 mm. (lower face) 



1 7<7.=0.08 mm. . N 



I 0.40mm. (upper face) 



Variation*. The exterior surface of a zoarium creeping on the roots of algae 

 is naturally larger than the surface in immediate contact with the substratum. 

 When the calcification is intense and the walls thick, the micrometric difference 

 for each zooecinm becomes perceptible, as we have established in this species. The 

 number of lateral areolae is about six; they are frequently above the aperture; 

 their place is inconstant, in no wise regular. The orbicular zoarium contains at 

 the center some zooecia somewhat different; they are erect and ornamented with 

 a large auriculated vibraculum; they arise from the exaggerated development of 

 one of the areolae (fig. 11). The perforations of the lower face of the zoarium 

 serve probably as a passage for radical fibers ; they are often surrounded by hollow, 

 hydrostatic tubcrosities (fig. 13). The tangential section (fig. 10) shows that the 

 olocystal elements of the frontal wall are grouped in lines radiating from the 

 aperture toward the areolae; perhaps a very compact pleurocyst covers the olocyst. 



Hippomenella radicata, and SchizoporeUa geminopora Eeuss, 1847, have also 

 some radicular pores on their lower face, but they belong to different genera easy 

 to differentiate. 



This species differs from Hippoporella multilamettosa in its unilamellar and 

 orbicular zoarium, in the absence of a separating salient thread, in the constant 

 presence of the pores, and in its transverse aperture. 



Occurrence. Vicksburgian (Glendon member of Marianna limestone) : West 

 bank of Conecuh Eiver, Escambia County. Alabama (common). 



Cotypes.C-At. No. 64272, U.S.N.M. 



HIPPOPONELLA, new genus. 



The operculum is contracted laterally. The ovicell is hyperstomial and 

 always closed by the operculum. The frontal is bordered with areolar pores. 

 Genotype. Hippoponella (Lepralia} hippopus Smitt, 1867. Eecent. 



Genus HIPPOMENELLA Canu and Bassler, 1917. 



1917. Ilippomenella CANU and BASSLER, Synopsis of American Eary Tertiary Cheilostome 

 Bryozoa, Bulletin 96, United States National Museum, p. 41. 



The aperture bears two small cardelles placed very low and separating a large 

 porta from a small vanna; it is always semielliptical (in the interior). The 

 ovicell, hyperstomial, is deeply imbedded in the distal zooecia ; it opens by a large 

 opening above the aperture, but it is never closed by the operculum. The frontal 

 is formed of an olocyst perforated laterally by some areolae and supporting a 

 pleurocyst more or less developed. The ovicell bears laterally two areas in the 

 form of a lunar crescent and more or less perforated. There are nearly always 

 spines and some avicularia. 



Genotype. Hippomenella (Lepralia} mucronelliformis Waters, 1899. 



Range. Lutetian-Becent. 



