NORTH AMERICAN LATER TERTIARY AND QUATERNARY BRYOZOA. 39 



SECTION III. OVICELL HYPEBSTOMIAL, ALWAYS CLOSED BY THE OPERCULUM. 

 Genus MEMBBANIPORIDRA Canu and Bassler, 1917. 



(For description, see Bulletin lOG, U. S. National Museum, p. 133.) 



MEMBRANIPORIDKA PARCA, new species. 



Plate 12, fig. 7. 



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



by a deep furrow, regularly elliptical; the frontal is formed of a convex gymnocyst 



principally developed in the inferior part of the zooecium. The opesium is regularly 



elliptical and beats a distal indentation in which the operculum is placed. The 



ovicell is convex, smooth, transverse, placed on the gymnocyst of the distal zooecium; 



it is always closed by the operculum. 



,, , r^ • [Ao = 0.30mm. „ . fi2 = 0.50mm. 



Measurements. — Upesia -, „ ,-,,^ Z,ooecia , ^ „. 



^ [w = 0.22 mm. 1/2 = 0.30 mm. 



Variations. — It is very difficult to interpret the operation of the operculum 

 on the fossds. Here the oviceU is indeed separated from the opesium by the mural 

 rim, but the superior indentation of the opesium which corresponds to the opercu- 

 lum is of exactly the same form as the orifice of the ovicell. It is therefore very 

 probable that our generic assignment is exact. 



This species rests directly upon the shell and does not secrete a calcareous 

 dorsal. This ecqnomy of calcite is rather rare in the strata which are not exclusiveh' 

 arenaceous. 



Occurrence. — Miocene (Choctowhatchee marl) : Jackson Bluff, Ocklocknee 

 River, 25 miles southwest of Tallahassee, Florida (very rare). 



Holotype.—C&i. No. 6S447, U.S.N.M. 



DIVISION IV. OVICELL NEVER CLOSED BY THE OPERCULUM. 

 Genus ALDERINA Norman, 1903. 



(For description, see Bulletin 106, U. S. National Museum, p. 140.) 



ALDERINA CESTICELLA, new species. 



Plate 12, figs. 4, 5. 



Description. — The zoarium incrusts oysters. The zooecia are distinct, elon- 

 gated, oval, separated by a deep furrow, ornamented by a short gymnocyst; the 

 mural rim is thin; enlarged behind in the form of a cryptocyst, rounded, sahent, 

 garnished with six to eight large distal spines; the opesium is anterior, oval, sur- 

 rounded by a sahent and fuiely wrinkled collar. The ovicell is large, salient, 

 globular, hemispherical, bearmg a large, inferior collar, transverse and linear. The 

 ancestrula bears an opesial smus. 



^ . f/io = 0.20-0.25 mm. „ ■ fi2 = 0.40-0.50 nam. 



ifea^wemenfe.-Opesiaj ^^ ^ q^^_qo2 mm. ^ooec^n^ ^^ ^ 0.25-0.30 mm. 



Affinities. — This species is irregular in its micrometric measurements, but the 

 zooecial form remains always pyriform. The ancestrula is quite remarkable. It 

 is eUiptical and deprived of spines. It engenders two large and three small zooecia. 

 Its opesium bears a deep sinus, the significance of which is unknown. The marginal 



