NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
517 
HASWELLIA GRACILIS, new species. 
Plate 66, figs. 8-10. 
Description. — The zoarium is free, cylindrical, slender. The zooecia are dis- 
posed all around the zoarium; they are quite long and indistinct; the frontal is a 
thick tremocyst with small, numerous pores. The peristome is salient, almost per- 
pendicular to the zoarium ; the peristomice is orbicular ; the peristomie is invisible 
exteriorly, but it is as long as the zooecia. The spiramen is a small, salient, oblique 
tube placed on the median zooecial axis just below the peristome. 
Measurements. — Apertura mm ‘ Zooecia. — Zs=0.75-1.50 mm. 
1 [la— 0.09 mm. 
Affinities. — In spite of its very simple structure this species lias necessitated 
long study. Success 
with the longitudinal 
sections (fig. 9) has 
permitted us to clas- 
sify it generically. 
The spiramen is 
higher than the peri- 
stomie and quite dis- 
tant from the aper- 
tura. 
This species much 
resembles the recent 
Porina proboscidea 
Waters, 1888. It dif- 
fers from it in its 
much smaller micro- 
metric dimensions 
and in its zooecia dis- 
posed all round the 
zoarium and not on 
one side alone. It 
sometimes has a small 
avicularium placed in 
the vicinity of the 
apertura. 
Occurrence. — Middle Jacksonian (Castle Hayne limestone) : Wilmington, North 
Carolina (very common). 
Holotype . — Cat. No. 64164, U.S.N.M. 
Genus SEMIHASWELLIA Canu and Bassler, 1917. 
1917. Semihaswellia Canu and Basslek, Synopsis of American Early Tertiary Clieilostome 
Bryozoa, Bulletin 96, United States National Museum, p. 58. 
The zooecia are disposed only on one side of the zoarium; the dorsal bears only 
avicularia. The frontal and the dorsal are of the same nature and are formed of 
a tremocyst with sulci. 
Fig. 151. — Genus Semihaswellia Canu and Bassler, 1917. 
A-C. Semihaswellia -prohoscidea Waters, 1889. A. Zoarium natural size. 
B. Fragment of branch with ordinary and ovicelled zooecia, X 25. C. Pos- 
terior face without zooecia, X 12. (A-C after Waters, 1889.) 
avd , dorsal avicularium; avf , frontal avicularium; ov, ovicell; pis , exte- 
rior orifice or peristomice, never closed by the operculum; s, sulci; sp, spi- 
ramen. 
