NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
473 
the peristomie. The small median avicularium is placed in the peristomie or in 
the peristomial sinus. 
i> r , -r, . , f h.pe= 0.06-0. 08 mm. 
Measurements . — Peristomice , 7 _ , , 
7^6=0.12-0.14 mm. 
Zooecia 
[ Lz—0. 56-0.60 mm. 
I 7,2=0.16 mm. 
Affinities . — This species differs from Plagiosmittia regularis in its smaller 
micrometric dimensions {Lz— 0.60 and not 0.75 mm.) and in its avicularium which 
is median. 
It differs from Plagiosmittia virgula in the absence of the large median 
avicularium, and in its smaller dimensions {Ls= 0.50 and not 0.56 mm.). 
Occurrence . — Middle Jacksonian: Wilmington, North Carolina (very com- 
mon) ; Eutaw Springs, South Carolina (common) ; near Lenuds Ferry, South 
Carolina (very common). 
Cotypes . — Cat. No. 64136, U.S.N.M. 
PLAGIOSMITTIA VIRGULA, new species. 
Plate 62, figs. 1-7. 
Description . — The zoarium is free, bilamellar; the fronds are narrow and 
bifurcated. The zooecia are elongated, elliptical, distinct, separated bv a furrow; 
the frontal is little convex and formed of a tremocyst with much crowded pores. 
The peristome is thin, salient, sharp ; the peristomice is oval ; the apertura is semi- 
lunar with a straight proximal border. The ovicell is large, little salient ; it is 
hyperstomial, imbedded in the distal zooecia, and opens largely into the peristomie; 
it is formed by a very finely porous circular area surrounded by a thin, little 
salient collar. The avicularium is median, placed in the peristomie; it is often 
developed and transformed into large unguiculate avicularia assuming the form 
of a comma. 
M casurements . — Peristomice 
Zooecia 
\hpe=0.1b mm. 
\lpe=0.10 mm. 
\Lz= 0.45-0.50 mm. 
1 7s=0.20-0.25 mm. 
Apertura 
ha = 0.10 mm. 
la = 0.10 mm. 
Affinities . — The large frontal avicularium is not always developed; it is 
replaced by a small peristomial avicularium. The difference between this species 
and Plagiosmittia porelloides is then very small ; only the micrometric dimensions 
are smaller (Lz=0 . 50 and not 0.60 mm.). The tangential section shows (fig. 4) 
that the median avicularium is often replaced by two peristomial avicularia. 
The three species of Plagiosmittia are distinguished quite well from each other 
by their zooecial length : 
Plagiosmittia regularise 0.75-1.00 mm. 
Plagiosmittia p orello i de s =0.5 6-0 . 6 0 mm. 
Plagiosmittia virgtila=0A5-0.50 mm. 
Occurrence . — Middle Jacksonian (Castle Hayne limestone) : Wilmington, 
North Carolina (very common). 
Cotypes.— Cat. No. 64137. U.S.N.M. 
