NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
737 
peristomie; the peristome is thin, elliptical. The ovicell is small, globular, little 
salient; the oeeiostome is not salient. It has no zone of growth. 
Diameter of the peristome 0.08-0.10 mm. 
,, , Distance of the peristomes 0.40 mm. 
Measurements . — 0 . , ' . , „ „„ 
reparation of the peristomes 0.40 mm. 
Length of the peristomie 0.10-0.16 mm. 
Affinities. — The zoarium appears as a disk garnished with points ; but we have 
not had the fortune to collect a single complete disk, for it seems extremely fragile. 
This species differs from Microecia vibrio in its free, orbicular zoarium and 
in its rectilinear, never serpentiform, zooecia. It differs from Plagioecia lamellosa 
not only^in the nature of the ovicell, but also in its smaller peristome (0.08 and 
not 0.12 mm.) and in its other dimensions, which are always smaller. The zoaria 
are absolutely identical. 
Occurrence. — Vicksburgian (Marianna limestone) : West bank Conecuh River, 
Escambia County, Alabama (rare). 
Cotypes . — Cat. No. 65399, U.S.N.M. 
EXOCHOECIA, new genus. 
Greek: Exoche , prominence; in allusion to the position of the ovicell. 
The ovicell is large, symmetrica] ; it is placed on the zone of growth which it 
grows beyond, forming a large exterior saliency ; the oeeiostome is small, anterior, 
elliptical, turned toward the base. 
Genotype. — Exochoecia rugosa, new species. Vicksburgian. 
EXOCHOECIA RUGOSA, new species. 
Plate 158, figs. 1-16. 
Description. — The zoarium is a reticulate Mesenteripora / it is formed of 
irregular lamellae, presenting a rounded fold opposite the zone of growth. The 
tubes are arranged in quincunx in the vicinity of the fold and in radial rows per- 
pendicular to the zone of growth on the rest of the zoarium; they are indistinct 
and ornamented with large overlapping wrinkles. The peristomes are orbicular 
or elliptical, almost adjacent in the lines. The ovicell is large, pyriform, suspended 
on the zoarial margins, ornamented with large, transverse, widely spaced wrinkles; 
the oeeiostome is small, elliptical, transverse, turned toward the base. 
,, , f Diameter of the peristomes 0.10 mm. 
Measurements . — - „ A n . 
| (Separation of the lines 0.24 mm. 
Y aviations. — We know that these reticulate zoaria result from the folding of 
a primitive berenicoid zoarium and from the bending back of the folded fronds 
at the top. One of the consequences of this bending back is that the axis of the 
peristomes no longer coincides with the axis of the median tubes which develop on 
the basal lamella and which appear at the zone of growth. The tubes opening 
laterally on the fronds are from preceding ramifications; the axis of the peristome 
is indeed that of their zooecium, but the lines of the peristome are oriented per- 
55S99— 20— Bull. 106 47 
