NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
717 
PLAGIOECIA DISCOIDEA, new species. 
Plate 155, figs. 12-17. 
Description. — -The zoarium is free, orbicular, with the form of true Discosparsa. 
The tubes are distinct, cylindrical, smooth, bent upward at their extremity, ar- 
ranged in regular quincunx; the peristome is elliptical, horizontal, thin. The zone 
of growth is hardly visible. 
Diameter of the peristome 0.12 mm. 
Distance between the peristomes 0.30 mm. 
Separation of the peristomes 0.32 mm. 
Zoarial diameters 4.00 nun. 
Measurements - 
We have not found an ovicell well enough preserved to figure. 
Affinities. — This species differs from the free forms of Plagioecia concreta in 
its zooecia regularly arranged in quincunx on the zoarial margins. 
Occurrence. — Vicksburgian (Marianna limestone) : One mile north of Mon- 
roeville, Alabama (common). 
Cotypes. — Cat. No. 65461, U.S.N.M. 
KEY TO DETERMINATION OF PLAGIOECIA AND BERENICEA. 
Most of" the species of Berenicea and Diastopora winch we have examined probably belong, • 
according to their exterior resemblances, to Plagioecia. We have therefore thought it necssary 
to combine them in the same key for determination. This will facilitate the identification of 
specimens coming from localities which have been studied. It is evident that such keys are 
purely artificial and that they can not serve as a basis for a natural classification. Moreover 
they are necessarily only approximations. 
1 
2 
3 
5 \ 
6 
7. 
8 
9 { 
Zoarium bilamellar 
Zoarium unilamellar 
Zoarium incrusting 
Zoarium composite 
Zoarium in thick, regular fronds 
Zoarium in thin lamellae 
Tubes marginate 
Tubes with large overlapping wrinkles— 
Tubes with thin widely spaced wrinkles 
Zoarium discoidal (Discosparsa) 
Zoarium not discoidal ( Diastopora ) 
4. 
8 . 
10 . 
Plagioecia subramosa. 
3. 
Plagioecia marginata. 
Plagioecia lobata. 
Diastopora striatisemota. 
5. 
6 . 
Tubes in quincunx on the borders 
Tubes in radial rows on the borders 
Tubes marginate 
Tubes not marginate 
Peristome of 0.20-0.24 mm 
Peristome of 0.14-0.16 mm., zooecia indistinct 
Peristome of 0.14 mm., tubes distinct 
Peristome of 0.12 mm., zoarium tubular 
Peristome of 0.12 mm., zoarium lamellar , 
Peristome of 0.10 mm 
The tubes are decorated with large overlapping wrinkles— 
The tubes are smooth or striated 
The tubes are very close together nearly adjacent 
The tubes are widely spaced 
Plagioecia discoidea. 
Plagioecia concreta. 
Plagioecia marginata. 
7. 
Diastopora magnipora. 
Plagioecia tulnfer. 
Plagioecia tuboedes. 
Diastopora tubiformis. 
Plagioecia lamellosa. 
Diastopora striatisemota. 
Berenicea undata. 
9. 
10 . 
11 . 
Diameter of the peristome=0.14 mm Berenicea stipata. 
Diameter of the peristome=0.10 mm Berenicea brevissima. 
