108 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
The inner face is but slightly concave; the radial ribs are smooth and perforated 
with some small scattered pores or ornamented with large tuberosities. 
r , . fZs=0.25 mm. 
Zooecium , n 
Variations. — The interzooecial sections show that the inner side is very thick and 
fibrous, and that between the tuberosities there are sometimes very narrow tubules 
(fig. 9). The tuberosities on the rows of the noncelluliferous face (figs. 10, 12) are 
not constant (fig. 11), and the same zoarium (fig. 10) shows both smooth and tuber- 
ous conditions. Gemmation about the ancestrula is not regular. It is linear at first, 
and the zoarium becomes discoidal by the special budding along lateral lines (fig. 10) . 
In tangential section (figs. 7, 13) the mural rim is seen to be formed of olocystal 
elements grouped in radial lines around the opesium. A tangential section of the 
inner face (fig. 6) shows olocystal nuclei corresponding to the tuberosities. The ribs 
are separated b} ? a white line. 
Affinities.- — The opesial collar is similar to that described by Levinsen in Mem- 
branicellaria / but we have not observed ovicells. 
This species differs from Otionella 'perforata in the tuberosities which ornament 
its noncelluliferous side and in its vibracula, which are larger than the zooecia. 
Occurrence. — Claibornian (Cook Mountain formation) : Moseleys Ferry, Cald- 
well County, Texas (rare). 
Lower Jacksonian (Moodvs marl) : Jackson, Mississippi (common). 
Jacksonian (Zeuglodon zone) : South side of Suck Creek, Clarke County, Mis- 
sissippi (rare). 
Cotypes. — Cot. No. 63811, U.S.N.M. 
Measurements- 
. \ho= 0.15 mm. 
-Opesium L 
nun. 
TT .. , \Lv=0.Z5 mm. 
Vibraculum , nnn 
\lv= 0.26 mm. 
OTIONELLA CAVA, new species. 
Plate 21, figs. 8-14. 
Description. — The zoarium is orbicular. On the outer surface the zooecia are 
arranged in regular quincunx lines. They are hexagonal, a little elongated, some- 
what indistinct, confluent through the union of their mural rims ; the mural rim is 
quite uniformly developed, thick, somewhat enlarged at the base. The opesium is 
elliptical, elongated, entire. The vibraculum is very large, twice as long as the 
zooecia, and is interzooecial, unsymmetrical and auriculated; its projecting lip is 
small. On the inner side the radial ribs are hollow and not calcified; the zooecial 
walls are pierced everywhere with small hydrostatic tuberosities. 
Measurements. — Opesium 
\ho= 0.26 mm. 
lfo=0.18 mm. 
Vibraculum 
|Z'y=0.65 mm. 
I Z-vj = 0.26 mm. 
Zooecium 
(Zs=0.35 mm. 
[fe=0.24 mm. 
Affinities. — The hydrostatic system of this species is strongly developed and is 
quite analogous to that of Lunularia distans Lonsdale, 1845. The external surface 
