394 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
Hippodiplosia ( Lepralia ) asperrima Reuss, 1847. Tortonian. 
Hippodiplosia ( Lepralia ) aperta Manzoni, 1874. Tortonian. 
Hippodiplosia ( Lepralia ) megaiota Reuss, 1847. Tortonian. 
Hippodiplosia ( Eschara ) ampla Reuss, 1847. Tortonian. 
Hippodiplosia ( Eschara ) hiauricidata Reuss, 1847. Tortonian, 
Hippodiplosia ( Eschara ) oculata Manzoni, 1871. Tortonian. 
Hippodiplosia granulosa Canu, 1915. Aquitanian. 
Hippodiplosia vemucosa Canu, 1915. Aquitanian. 
HIPPODIPLOSIA VESPERTILIO, new species. 
Nate 52, figs. 5-12. 
Description. — The zoarium is free, formed of two lamellae fused together and 
inseparable; the fronds are narrow and bear 4 to 6 longitudinal rows of zooecia. 
The zooecia are long, 
distinct, sinuous, clavi - 
form; the frontal is 
convex; it is a thick 
tremocyst with tu- 
bules resting on a 
very thin, perforated 
olocyst. The aper- 
ture is elliptical, elon- 
gated, provided with 
two very small, in- 
constant cardelles. 
The ovicell is globu- 
lar, little salient, little 
imbedded in the distal 
zooecia, closed by the 
operculum w h e n it 
opens; it is surround- 
ed by areolae. Two 
Fig. 117. — Genus Hippodiplosia Canu, 1916. 
A-F. Hippodiplosia pallasiana Moll, 1803. A. Ordinary zooecia, X 30. 
B. Ovicelled zooecia, X 20. (A, B after Hincks, 1880.) C. Young 
zooecium, X 40. D. Multiporous septula. E. Distal wall, X 20. F. 
Lateral wall, X 20. (C-F after Levinsen, 1894.) 
tubular symmetrical avicularia open on each side of the aperture. 
M easurements 
fAa= 0.15 mm. 
-Aperture , , 
I /tt=0.11 mm. 
„ . r Lz= 0.60-0.75 mm. 
Zooecia . 00 
[lz=0.2>2> mm. 
Variations. — In the interior (fig. 9) the aperture is oblique; the tubules are 
visible by transparency through the very thin olocyst. The longitudinal section 
(fig. 7) shows zooecial alternation due to the closeness of the border of the zoarium ; 
there is a large distal septula and we are able to verify five or six lateral septulae. 
The longitudinal section (fig. 10) indicates that the operculum ought to close the 
ovicell in opening, although we cannot be rigorously certain of this. It is evident 
that if the ovicell was closed by a special membrane, it would be necessary to create 
