NORTH AMERICAN EARLY TERTIARY BRYOZOA. 107 



~ . [A0=0.12 mm. . \Ls=0.-2o mm. 



Measurements, Opesium' . , /ooecium 7 -.on nor- 



|Z0=0.10 mm. [te=0.20-0.2< r 



., , |Zy=0.25 mm. 

 Vibraculum ,, 



^ 

 mm. 



mm. 



Variations. The lines of zooecia are easily detached from one another. Their 

 edge (fig. 16) shows a minutely furrowed surface in which the furrows radiate 

 from the same center of origin as the lines. As is indicated in figures 11, 12, 13 

 this center of origin is not necessarily the zoarial center. These furrows represent 

 intercostal canals which are independent of the perforating tubules (fig. 19), the 

 orifices of which are visible at t in fig 16. This same figure shows also the large 

 multiporous lateral septulae. 



In sections (fig. 19) the zooecia are urceolate, erect, separated by convex par- 

 titions. In the same radial line they communicate among themselves by means of 

 a large distal septula (s. d.}. The tubules (t), corresponding to the large pores of 

 the inner face, probably serve for the passage of the mesenchymatous network. 



In small zoaria the ribs of the inner face are hollow at their extremities (figs. 

 13, M, 15). These, hollow spaces were subsequently filled up, for the sections do not 

 indicate these cavities (fig. 19). 



The proliferation of the zooecia is not always regular about the ancestrula (fig. 

 14). A nabelliform colony (fig. 13) is often formed and becomes discoidal by 

 special budding at the ends and on the sides of the lines of zooecia. The tangential 

 section (fig. 17) is not very well oriented, but it is sufficient to show the constitu- 

 tive elements of the olocyst grouped in radial lines about the opesium. 



Affinities. This species differs from Otionella tuberosa in the numerous pores 

 which perforate its inner face. The opesial collar is analogous to that which Levin- 

 sen has noted in Membranicellaria; but we have never observed the endotoichal ovi- 

 cell of this genus. 



Occurrence. Claibornian (Gosport sand) : Claiborne, Alabama (common) ; 

 Gopher Hill, Tombigbee River, Alabama; 1 mile southeast of Rockville, Clarke 

 County, Alabama (common). 



Claibornian (Lisbon formation) : Wautubbee Hills, 4 miles south of Enterprise, 

 Mississippi (rare). 



Lower Jacksonian (Moody.s marl) : Jackson, Mississippi (common). 



Cotypes.Crt. No. 62571,' U.S.N.M. 



OTIONELLA TUBEROSA, new species. 



Plate 12, figs. 5-15. 



Description. The zoarium is discoidal, with a concave inner face. The zooecia 

 are hexagonal, somewhat indistinct, joined by their mural rims, disposed apparently 

 in irregular quincunx ; the mural rim is concave, broad, especially at the base. The 

 opesium is elliptical or nearly orbicular and bordered by a prominent collar. The 

 vibraculum is interzooecial, asymmetrical, auriculated, larger than the zooecium. 



