Bulletin - United States National Museum - Smithsonian Institution

38 BULLETIN 9C, UNITED STATES NATIONAL MUSEUM.
GASTROPELLA VENTRICOSA, new species,
riate 4, fig. 3.
Description.—The zoariiim is free, cylindrical, bifurcated. The
zocecia are large, elliptical, swollen; the frontal is smooth, conA^ex,
garnished laterally with some large areolae. The ascopore is very
large, not salient, placed in the upper third of the zocecia. The
peristome is salient and sharp; the peristomice is oblique, orbicular
or elliptical. The ovicell is entirely hidden within the thickness of
the frontal of the distal zocecium.
. . [A »e= 0.10-0.15 mm.
Measurements.—Feristomice , ^.^f,
[Ipe =0.15 mm.
Zs=0.85 mm.
Zocecia ^ , ^ , ^
\lz =0.40 mm
Affinities.—There is frequently a very small peristomial avicu-
larium. On the longitudinal sections the ascopore manifestly opens
below the apertura and it often appears like a large funnel. On the
ovicelled zocecia there is a sort of clamp which is perhaps intended
to fasten the operculum during the expulsion of the larva.
Occurrence.—Midwayan: Mabelvale near Little Eock, Arkansas
(common).
Type.—Q^i. No. 62589, U.S.N.M.
Family HIPPOTHOIDAE Levinsen, 1909.
The zocecia become calcified from behind in successive zones forward,
leaving at the surface more or less salient lines, the lines of
growth, and are furnished Avith a variable number of dietellae.
The genera of this family are as follows, those represented in
American deposits being marked with an asterisk.
* Eippothoa Lamouroux, 1821. Lutecian-Eecent.
Chorizopora Hincks, 1880. Eecent.
* Trypostega Levinsen, 1909. Jacksonian-Eecent.
Haplopoma Levinsen, 1909. Tortonian-Eecent.
Dacryopora Lang, 1914. Cenomanian-Senonian.
Family ESCHAEELLIDAE Levison, 1909.
The ovicell is hyperstomial. The operculum is rigid and chitinous
; it closes the aperture, the compensatrix, and often the ovicell
its form is in rapport with the hydrostatic system, and the passage
of the eggs into the ovicell.
This family is the reunion of the old families of Microporellidae,
Myriozoidae, and Escharidae (part) of Smitt and Hincks. Levin-
;