NORTH AMERICAN LATER TERTIARY AND QUATERNARY BRYOZOA. 137 



stomial, very globular, smooth, costulated on its borders; it is closed by the opercu- 

 lum. A very small median avicularium opens in the apertura. 



-,, , i . f7ia = 0.15mm. „ . fZ3 = 0..50mm. 



Measurements. — ^Apertura , „ ,„ Zooecia , „ „, 



^ (/a = 0.12 mm. ( /2 = 0.35 mm. 



Variations. — The exterior aspect of this species is rather variable. Figure 12 

 represents the young zoarium which has not had time to attain its complete develop- 

 ment. The apertura appears as elliptical and elongated; the frontal is still not 

 completely covered by the pleurocyst and the deposit of calcite is clearly visible 

 around each areolar pore. In figure 13 the calcification is complete; the frontal is 

 very thick and the form of the apertura here becomes undefinable. The small 

 median avicularium appears to be excavated in the thickness of the pleurocyst. 



Occurrence. — Miocene (Yorktown formation) : 1 mile west of Fort Nonsense, 

 Gloucester County (rare), Beulahland, King and Queen County, and other localities 

 in Virginia (rare) . 



Cotypes.—Cnt. No. 68619, U.S.N.M. 



Genus CYCXOPERIELLA Canu and Bassler, 1920. 



1920. Cycloperiella Canu and Ba.ssler, Monograph North American Early Tertiary Bryozoa, 

 Bulletin 106, U. S. National Museum, p. 43. 



The dvicell is hyperstomial, globular, not embedded in the distal zoecium, 

 and entirely covers the apertura. The apertura is formed of a semilunar anter 

 and of a very concave poster. The frontal is formed of a very thin olocyst; sup- 

 porting a tremocyst with large widened pores. 



Genotype. — Cycloperiella rubra, new species. 



Range. — Miocene-Pliocene. 



This genus offers the same frontal and apertural characters as Cyclicopora 

 Hincks, 1884. It differs from it in its ovicell never closed by the operculum. 

 The passage of the eggs is assured by the form of the ovicell itself, which entirely 

 covers the apertura. 



CYCLOPERIELLA RUBRA, new species. 



Plate 21, figs. 5-9. 



Description. — The zoarium incrusts shells and frequently presents two super- 

 posed lamellae. The zooecia are elongate, a little elliptical, separated by a deep 

 furrow; the frontal is thick, convex, and covered with large, widened tremopores. 

 The apertura is semilunar, with a concave proximal border, and surrounded by 

 a sort of thick and little salient peristome. The ovicell is globular, salient, covered 

 with tremopores; it entirely covers the apertura. Its exterior orifice is irregular. 



,, ^ » ^ lha = 0.l5 mm. „ . (£2 = 0.55-0.60 mm. 



Measurements. — Apertura , ^,. Zooecia, „ „. 



^ [ia =0.1o mm. [Iz =0.35 nmi. 



Affinities. — The zoarium often covers large surfaces; it was strongly pigmented, 



all the fossils are purple, indicating that their primitive tint was red. In the 



interior the very thin and pellicular olocyst scarcely resists fossilization, and the 



tremopores are clearly visible. Two very small lateral condyles serve as axis to 



the operculum. The orifice of the ovicell is irregular, oblique to the zooecial 



surface. It is difficult to comprehend how the polypide could extend its tentacles. 



12184— 23— Bull. 125 10 



