396 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
distinct, elongated, elliptical; the frontal is convex and formed of a thick tremocvst 
with large tubules resting on a very thin perforated olocyst. The aperture is 
elliptical, somewhat elongated; the anter is separated by two very small cardelles 
from a poster somewhat smaller. The avicularium is long, thin, provided with a 
pivot; it is placed laterally under the aperture; the beak is falciform. The old 
zooecia are indistinct. 
Measurements . — Aperture 
fAa=0.15 mm. 
I /a=0.12 mm. 
Zooecia 
{ Lz— 0.60-0.70 mm. 
I lz= 0.30-0.35 mm. 
Affinities . — Only the two figured specimens have been found; apparently the 
proliferation of this species does not correspond to the zoarial vigor. In the old 
zooecia the tubules are very long; the avicularia immersed between them are hardly 
visible. 
The species differs from HippodipWsia vespertilio in the presence of its large 
falciform avicularium, which attains a length of 0.35 mm. 
Occurrence . — Middle Jacksonian (Castle Hayne limestone) : Wilmington, North 
Carolina (very rare). 
Cotypes.— Cat. No. 61096, U.S.N.M. 
HIPPODIPLOSIA MAGNIPOROSA, new species. 
Plate 87, figs. 7-9. 
Description . — The zoarium is hollow, cylindrical, branched, unilamellar, rarely 
plurilamellar ; it incrusts small algae. The zooecia are little distinct', elongated, 
almost cylindrical; the frontal is a tremocyst with large funnel-shaped pores rest- 
ing on an olocyst perforated by small corresponding pores. The aperture is almost 
orbicular and formed of a large anter separated from a small concave poster by 
two very salient, triangular cardelles; the peristome is often very wide, smooth, 
and very little salient. The ovicell is embedded in the distal zooecium, it is 
liyperstomial and opens above the aperture by a thin slit; it is of the same 
nature as the frontal. Often the coalescence of two tremopores determines the for- 
mation of a small lateral avicularium with pivot. 
Measurements . — Aperture 
[7a=0.20mm. 
1 =0.1 5 mm. 
Zooecia 
7,2=0.75 mm. 
7.3=0.40 mm. 
Variations . — The lateral avicularium is very inconstant. The young zooecia 
(fig. 7) have a thin peristome, somewhat prominent in front. Sometimes the 
tremocyst is detached from the underlying olocyst (fig. 9). 
Affinities . — This species differs from Hippodiplosia petiolus Lonsdale. 1845, 
in its hollow zoarium and its shorter zooecia. 
It differs from Hippodiplosia strangulata in its shorter aperture and in the 
absence of a peristomial avicularium. 
Occurrence . — Vicksburgian (Marianna limestone) : Salt Mountain, 5 miles 
south of Jackson, Alabama (rare). 
Vicksburgian (Red Bluff clay) : Seven and one-half miles southwest from 
Bladen Springs, Alabama (rare). 
Cotypes. — Cat. Nos. 64278, 64279, U.S.N.M. 
