156 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
CALLOPORA MUNDULA, new species. 
Plate 29, fig. 12. 
Description. — The zoarium is bilamellar, free, composed of large, flat fronds; 
the two lamellae are back to back and inseparable. The zooecia are large, elongated, 
distinct, separated by a deep furrow ; the mural rim is thin distally, enlarged 
proximally, rounded or angular. The opesium is regular, elliptical, elongated. 
The ovicell is globular, salient, smooth ; it is hyperstomial and opened in a special 
orifice above the operculum. The avicularium is frontal, large, elliptical with two 
lateral denticles. 
Measurements. — Opesia 
Affinities. — This neat and elegant species appears to be the largest species of 
C allop ora. In general aspect it approaches Grammella transversa; it differs from it 
in the longitudinal and non-transverse orientation of its avicularium and its bifoli- 
ate and not incrusting zoarium. 
Occurrence. — Lower Jacksonian (Moodys marl) : Jackson, Mississippi (rare). 
Holotype.— Cat. No. 63928, U.S.N.M. 
Genus AMPHIBLESTRUM Gray, 1848. 
184S. Ampliible strum Gkay, List British Animals British Museum, Centroniae, pp. 110, 146. 
1903. Amphiblestrum Nokman, Notes Natural History East Finmark, Annals and Magazine 
Natural History, ser. 7, vol. 11, p. 596. 
Hinder portion of the area covered with a calcareous crust. In front of this a 
considerable portion of the area, typically trifoliate, but sometimes semielliptical 
or subrotund, is covered only Tv a thin membrane, at the distal extremity of which 
is situated the simple oral opening. Margin of zooecium thickened, often granu- 
lated, sometimes bearing a pair (or more) of lateral spines found in young speci- 
mens. Reproduction by means of prominent hyperstomial ovicells never closed by 
the operculum. Sessile avicularia often present, sometimes one, sometimes two, 
on the hinder portion of the zooecium. Dietellae, two pairs of lateral and one distal. 
(After Norman.) 
Genotype. — Amphiblestrum ( Membranipora ) flemingii Busk, 1852. 
Range. — Senonian-Recent. 
This is in part the Membranipora flemingii group of Waters which he defined as 
follows : “ Ovicells with more or less arched area on the front ; usually lamina over 
considerable part of the front. Pore chambers/’ 
The opesium often appears trifoliate. The distal part is occupied by the- oper- 
cular valve for which the opesial contraction serves as a pivot. The proximal por- 
tion, which is the larger, is occupied by the chitinous part of the cryptocyst on which 
the parietal muscles are inserted. The calcareous crvptocyst, the chitinous crypto- 
cyst, and the opercular valve form a structure in direct contact with the ectocyst. 
The entire structure is covered by a thin ectocyst united at the opercular valve 
which is thus thickened and often bordered with a sclerite. Between the chitinous 
|k=0.55 mm. . | Zs= 0.75-1. 00 mm. 
|Z?=0.28 mm. ^ 0CKCia 1^=0.35-0.40 mm. 
