NORTH AMERICAN LATER TERTIARY AND QUATERNARY BRYOZOA. 35 



SECTION II. MEMBRANIPORAE WITH ENDOZOOECIAL OVICELL. 

 Genus VIBRACELLINA Canu and Bassler, 1917. 



(For description see Bulletin 106, U. S. National Museum, p. 110.) 



VIBRACELLINA PUSILLA, new species. 



Plate 10, figs. 4, 5. 



Description.— The zoarium incrusts shells. The zooecia are small, oval, a little 

 elongated, distinct, separated by a deep furrow; the mural rim is thin, rounded, 

 salient, much enlarged at the base into a concave cryptocyst. The opesium is 

 anterior, oval, regular. The ovicell is very small and endozooecial. The vibracula 

 are small, salient, elliptical, auricular. 



Measurements. — Opesia 



f/io = 0.14-0.16 mm. ^ . fL2 = 0.30mm 



Zo = 0.10mm. [ ^2 = 0.14 mm. 



Affinities. — According to the rule in this genus, the ancestrular zooecia are 

 smaller and frequently calcified. The ancestrula engenders five normal zooecia 

 and three vibracular ones. In the proximal portion of the zooecia there is often a 

 very short gymnocyst. 



This species differs from Membrendoecium rectum Canu and Bassler, 1920, from 

 the Vicksburgian in its slightly smaller dimensions, its concave and not flat crypto- 

 cyst and in its nonsalient mural rim. 



Occurrence. — Pliocene (Caloosahatchee marl) : Shell Creek, De Soto County, 

 Florida (very rare) . Miocene (Duplin marl) : Natural well, 2 mUes southwest of 

 MagnoHa, North Carolina (rare) . 



Cotypes.—Cs,t. Nos. 68435, 68436, U.S.N.M. 



VIBRACELLINA SIMPLEX, new species. 



Plate 10, figs. 6, 7. 



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



by a furrow, elongated, pyriform; the gymnocyst is smooth, convex, rather short; 



the termen is sharp. The opesium is oval, the point above. The ovicell is very 



small and endozooecial. The vibracula are rare, very small, auriculated. The 



ancestrula is calcified and presents a small semilunar aperture. 



,, . ^ • f/io = 0.20mm. „ . fL2 = 0.35-0.40 mm. 



Measurements. — Upesia , r% m ^ ic Z,ooecia , 



^ 1 10 = 0.13-0.15 mm. [t2 = 0.2omm. 



Structure. — The rarety of vibracula give to this species an aspect of great 

 simplicity. The heterozooecia appear to be zooecia in which the development has 

 been arrested by adjacent zooecia. The ancestrula and three ancestrular zooecia 

 are calcified. The hexagonal symmetry in the arrangement of the ancestral zooecia 

 is remarkable. Nevertheless, there are really only five zooecia issuing from the 

 ancestrula according to the rule, and no vibracula. We have observed calcified 

 zooecia and also regenerated zooecia in vicinity of the ancestrula. 



This species differs from Vihracellina pusilla in its larger micrometric dimen- 

 sions and in the very great rarity of the vibracula. 



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

 25 miles southwest of Tallahassee, Florida (very rare). Miocene (Duplin marl): 

 Natural well, 2 miles southwest of Magnolia, North Carohna (rare). 



Cotypes.—C&t. Nos. 6S437, 68438, U.S.N.M. 



