NORTH AMERICAN LATER TERTIARY AND QUATERNARY BRYOZOA. 121 



Affinities. — The intensity of the calcification is remarkable in tfiis species 

 and gives to it an aspect very characteristic and difficult to figure. The large 

 aviculariuna is triangular, the beak pointing upward; the pivot is almost always 

 broken. The distal border of the apertura is often denticulated by the rupture 

 of the hollow spines much wider than the peristome. In spite of its double pro- 

 tective envelope the oviccll is often broken. The exterior aspect is absolutely 

 unique. Tliis species must have lived in a strong current. 



Occurrence. — Miocene (Duplin marl) : Darlington Courthouse, South Carolina 

 (rare) . 



Hohtype.— Cat. No. 68591, U.S.N.M. 



MICBOPORELLA BIFOLI4TA Ulrich and Bassler, 1904. 



Plate 20, figs. 7-11. 



1904. MicropoTellal bi/oliata Ulrich and Bassleh, Maryland Geological Survey, Miocene, p. 417, 

 pi. 113, figs. 6-8. 



The original description is as follows : 



Zoarium erect, bifoliate, not known to branch. Zooecia subquadrate or hexagonal, arranged in 



regular longitudinal and diagonally intersecting series, four longitudinally and five diagonally in 2 



mm. Appearance of surface varjdng with age. In young examples the zooecia are more or less convex 



and separated, especially transversely, by an impressed line containing one or more rows of pores; 



the orifice is somewhat transverse and subovate with the proximal side straightened, the peristome 



but little elevated, the front sparsely punctated, the avicularia of which there is usually one to each 



zoOecium placed some distance beneath and to one side of the orifice, rather large, subcircular and 



di\dded into two nearly equal parts by a thin partition. In old examples the oral part is sunken and 



the rest of the surface abundantly punctate, while the a\dcularia have been somewhat reduced in size. 



Immediately behind the orifice there is always a small (? peristomial) pore. 0\-icells large, rather 



strongly convex, punctate. 



, . , fAa = 0.11 mm. „ . [^2 = 0.55 mm. 



Measurements. — Apertura, _ ,_ Aooecia , _ „r n-ic^r^ 



^ lia = 0.12mm. [te = 0.25-0.35 mm. 



We have notliing to add to the original description except to call attention 

 to the fact that the ascopore is crescent shaped. 



Tliis species differ from Microporella ciliata Linnaeus, 1759, in the absence of 

 frontal granules, in the presence of larger tremopores and in its nontransverse 

 aperture which is almost as high as wide. The erect form of the zoarium is rather 

 rare in the genus Microporella and it appears to form a good character for this 

 species. Nevertheless we have observed bilamellar expansions in Microporella 

 ciliata. 



Occurrence. — Miocene (Choptank formation): Cordova, Maryland (rare). 



Cotypes.— Cat. No. 68592, U.S.N.M. 



MICROPORELLA FISSURIFERA, new species. 



Plate 19, figs. 12-13. 



Description. — The zoarium incrusts shells. The zooecia are distinct, separated 

 by a deep furrow, cUiptical, little elongated, wide; the frontal is convex and per- 

 forated by a large nmnber of tremopores. The apertura is semilunar, transverse; it 

 is surrounded by a thin peristome bearing four large spines. The ascopore is placed 

 12184— 23— Bull. 125 9 



