376 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
anter separated b} 7 two large cardelles from a convex rather large poster; it is 
surrounded by an incomplete peristome bearing 6 large spines. The ovicell is 
prominent, globular, smooth ; it opens above the aperture. The avicularian zooecia 
are provided with a long, thin beak rounded at the extremity. 
Measurements. — Aperture 
A«.= 0.10 mm. 
la= 0.07 mm. 
Zooecia 
(Lz=0A0 mm. 
{fe= 0.25-0.30 
mm. 
Affinities. — The avicularian zooecia are very interesting; the beak develops 
around the aperture which does not preserve its form. The extensor muscle of 
the mandible passes by a sort of very narrow rimule (fig. 19) or by a wider one 
(fig. 18 ). 
Such transformations exist in the Celleporidae. Waters noted very similar 
avicularian zooecia in Holoporella pigmentaria Waters, 1909. 1 
Another interesting peculiarity is the complete absence of dorsal olocyst, easy 
to see on the broken zooecia of figure 19. This economy of calcification is rather 
frequent on the incrusting species. This new species differs from Hippoporina 
lucens and Hippoporina porcellana Busk, 1860 ( =Lepralia cleidostoma Smitt, 
1872), in the presence of avicularian zooecia and the absence of frontal avicularia. 
Cotypes.— Cat. No. 63824, U.S.N.M. 
Occurrence. — Midwayan (Clayton limestone) : One mile west of Fort Gaines, 
Georgia (rare). 
HIPPOPORINA LUCENS, new species. 
Plate 48, figs. 15-17. 
Description. — The zoarium incrusts shells. The zooecia are small, distinct, 
ovoid; the frontal is smooth, convex, polished. The aperture is elongated; the 
almost circular anter is separated by two large cardelles from a poster rather wide 
and straight. The ovicell is globular, salient, smooth ; it is hyperstomial and opens 
above the aperture by an arched crescent shaped slit. The avicularium is very 
salient; its mandible is nearly perpendicular to the zooecial plane; it has a cal- 
careous pivot. 
Measurements. — Aperture 
f ha— 0.10-0.12 mm. 
\la= 0.09-0.10 mm. 
Zooecia 
lLz= 0.36-0.40 mm. 
\lz— 0.20-0.24 mm. 
Variations. — The avicularium is very inconstant; it does not exist on all 
zooecia; its rupture causes the formation of an irregular cavity (fig. 15). The 
ovicell is formed of two calcareous lamellae perfectly distinct when broken (fig. 
17). The frontal also becomes covered with a more or less granulated calcareous 
deposit (figs. 15, 16) of the origin of which we are ignorant. 
Affinities. — This species is very close to Hippoporina cleidostoma Smitt, 1872 
(=77. porcellana Busk, 1860), which is still living in the regions of Madeira and 
Florida. It differs from it in the position and form of its avicularium and the 
much smaller width of its aperture (0.09-0.10 mm. instead of 0.10-0.13 mm. men- 
1 Reports on the Marine Biology of the Sudanese Red Sea, XII, Journal Linnean Society, vol. 31, p. 163, 
pi. 17, fig. 22. 
