NORTH AMERICAN EARLY TERTIARY BRYOZOA. 569 



The zooecia are elongated, distinct, elliptical, surrounded by numerous parietal 

 areolae. The cribriform area is wide, perforated by at least seven stellate pores. 

 The peristome is much developed above the aperture and caps the zooecia with a 

 large convexity, supporting a small, round avicularium. The aperture is trans- 

 verse and semielliptical; the peristomie is quite deep. At the base of each zooecium 

 there is a small, simple, adventitious, very salient avicularium. 



. fZs=0.45-0.52mm. 

 Measurements. Zooecia,, -. 



173=0.25 mm. 



Width of the peristomice=0.14 mm. 

 Length of the total area=0.15-0.20 mm. 



Variations. Our description is based on young zooecia (fig. 2). Quite fre- 

 quently the development of the pleurocyst reunites in a single total area the aper- 

 ture, median avicularium, and the cribriform area. 



The median avicularium normally round, is more elongated and pointed if 

 it be deeply imbedded (figs. 3, 4). The small distal avicularium is not very con- 

 stant on the old zooecia (fig. 6). The adventitious avicularium is less prominent on 

 the old zooecia, but it remains visible (fig. 7). The distal thickening of the peri- 

 stome which caps most of the zooecia disappears at the base of the old fronds 

 (figs. 4, 6). 



The older zooecia as usual lose their polypide and consequently their hydro- 

 static system. They contain only parietal areolae and avicularia (fig. 6). The 

 latter persist even after regeneration. 



There are sometimes two and three pores on the distal part of the prominence 

 above the zooecia (figs. 2, 3). 



The longitudinal section (fig. 10) shows very well the identity in structure of 

 this fossil form with that of the recent species so well figured by Waters. The 

 depth of the vestibule accounts for the invisibility of the aperture. 



The tangential thin section (fig. 8) indicates that the pleurocystal elements 

 are rather large. 



Affinities. The old zooecia are exactly like those of Adeonellopsis cydops, 

 but the young zooecia differ from that species in their zooecial cap and in the fact 

 that they lack a thin peristome. 



Adeonellopsis galcata differs from A. quisenberryae in its median avicularium, 

 which is straight and which never touches the walls of the total area. 



It differs from Adeonellopsis magniporosa in the distal thickening of its 

 peristome and the presence of a small distal avicularium. 



Occurrence.- Vicksburgian (Byram marl): Byram, Mississippi (common). 



Vicksburgian (Marianna limestone) : Two and one-half miles north of Millry, 

 Washington County, Alabama (rare) ; Deep well, Escambia County, Alabama. 



Vicksburgian (Red Bluff clay) : Red Bluff, Wayne County, Mississippi (rare). 



Cotypes.Cat. No. 64318, U.S.N.M. 



