NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
493 
It differs from Porella jacksonica in its zoarial fronds not spread out and 
very narrow, in its much wider umbo and in its still larger tremopores. 
Occurrence . — Vicksburgian (Byram marl) : Byram, Mississippi (very rare) ; 
one- fourth mile west of Woodward, Wayne County, Mississippi (common). 
Ilolotype. — Cat. No. 64303, U.S.N.M. 
Geological distribution of American species of Porella. 
Jacksonian. 
Name. 
Claiborn- 
ian. 
Lower 
Jackson- 
ian. 
Middle Jacksonian. 
Wilming- Rich Hill 
ton zone. zone. 
Upper 
Jackson- 
ian. 
Vicks- 
burgian. 
Porella obliqua, new species 
Porella irregularis, new species.. . 
Porella granulosa, new species . . . 
Porella coronata, new species 
Porella portentosa, new species. . . 
Porella aenticulif era, new species. 
Porella jacksonica, new species. . . 
Porella pungens, new species 
Porella unguiculata, new species . 
Porella crassoparies, new species . 
Porella abdita, new species 
Porella planulata, new species . . . 
Porella cylindrica, new species . . . 
Porella erecta, new species 
Porella compacta, new species 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
ANALYTICAL KEY TO AMERICAN SPECIES OP PORELLA. 
Zoarium vincular Porella 
I Zoarium incrusting 2 
j Zoarium escharian 5 
Zoarium unilamellar ; 10 
I Avicularium median, triangular Porella 
Avicularium quite salient on umbo i Porella 
Avicularium little salient 3 
f Avicularium adventitious on the peristome 
[Avicularium not adventitious on the peristome 
^(Frontal granular 
[No granules, zooecia irregular 
f Avicularium median, very salient on umbo 
[Avicularium small, not salient 
^[Umbo nearly straight : 
[Avicularian umbo oblique ; 
I Avicularian umbo large and short . 
Avicularian umbo thin, denticulate, very large tremopores__ 
Avicularian umbo thin, tremopores 
^[Large zooecia (Ls=1.10 mm.), avicularia invisible 
[Smaller zooecia 
[Frontal with separated tremopores 
J [Frontal with adjacent tremopores ; avicularia hardly visible. 
f Large avicularian umbo very salient 
1 [Avicularium not salient, small 
Porella 
_ 4 
Porella 
Porella 
-6 
-8 
Porella 
._7 
_ Porella 
— Porella 
_ Porella 
._ Porella 
-9 
Porella 
_. Porella 
._ Porella 
— Porella 
cylinclrica. 
obliqua. 
pungens. 
coronata. 
granulosa. 
irregularis. 
erecta. 
compacta. 
denticulifera. 
jacksonica. 
planulata. 
portentosa. 
abdita. 
unguiculata. 
crassoparies. 
