NORTH AMERICAN EARLY TERTIARY BRYOZOA. 473 



the peristomie. The small median avicularium is placed in the peristomie or in 

 the peristomial sinus. 



T,, fAe=0.06-O.OSmm . fis=0.56-0.60 mm 



Measurements. Penstomice , ^ "' Zooecia , 



4 mm. Us=0.16mm. 



Affinities. This species differs from Plagiosmittia regularis in its smaller 

 micrometric dimensions (Lz=Q.6Q 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). 



Cotypcs.Ciit. 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 by 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. 



. . . pe=.mm. (a = .mni. 



Measurements. Penstomice . Apertura , 



\lpe=O.W mm. [ la = 0.10 mm. 



. (Zs=0.45-0.50mm. 

 Zo0ecia !fe=0.20-0.25mm. 



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 (Lz0.5Q 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, regularisQ.lS'l.OQ mm. 



Plagiosmittia porettoides=Q.56-O.QO mm. 



Plagiosmittia mrffula=0.4:5-0.50 mm. 



Occurrence. Middle Jacksonian (Castle Hayne limestone) : Wilmington, 

 North Carolina (very common). 



Cotypes.Cnt. No. 64137, U.S.N.M. 



