Measurements.- 



NORTH AMERICAN EARLY TERTIARY BRYOZOA. 737 



peristoinie; the peristonic is thin, elliptical. The ovicell is small, globular, little 

 salient; the oeciostome is not salient. It has no zone of growth. 



Diameter of the peristome 0.08-0.10 mm. 



Distance of the peristomes 0.40 ram. 



Separation of the peristomes 0.30 mm. 



Length of the peristoinie 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). 



GotypesJC&t. No. 65399, U.S.N.M. 



EXOCHOECIA, new genus. 



Greek: Exoche, prominence; in allusion to the position of the ovicell. 



The ovicell is large, symmetrical ; it is placed on the zone of growth which it 

 grows beyond, forming a large exterior saliency; the oeciostome is small, anterior, 

 elliptical, turned toward the base. 



Genotype. Exochoccia i^ugosa, new species. Vicksburgian. 



EXOCHOECIA RUGOSA, new species. 



Plate 158, figs. 1-10. 



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 oeciostome is small, elliptical, transverse, turned toward the base. 



f Diameter of the peristomes - 0.10 mm. 



Measurements. ,. , ,. ,. 



| Separation of the lines _ 0.24mm. 



Yiu'liitions. 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- 

 5589920 Bull. 106 47 



