292 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
small vestibule. The two small oral avicularia 
without pivot. 
Measurements . — Aperture f 
I la— 0.10-0.11 mm. 
are peristomial, simple, and 
Zooecia 
f 7,s=0.40-0.45 mm. 
173=0. 30—0.35 mm. 
Variations . — The general effect of the lacunae gives to the zooecia a very char- 
acteristic warty aspect. These small ornaments are very fragile; they are much 
attenuated by fossilization, which gives the species such a very variable aspect. It 
is likewise often difficult to perceive the costular radiations. 
On the proximal lip of the aperture there is often a convex sinuosity or a kind 
of indistinct mucro. 
The lumen line is rarely visible (fig. 14). 
Affinities .- — This species differs from Cribrilina rathbunae in its larger dimen- 
sions, its more prominent lacunae, and its more regular zoarial margins, 
Occurrance . — Midwayan (Clayton limestone) : Mabelvale, near Little Rock, 
Arkansas; Luverne, Crenshaw County, Alabama (common) ; 1 mile west of Fort 
Gaines, Georgia (common) ; Brundige, Alabama (common). 
Cotypes. — Cat. Nos. 63811, 63812, U.S.N.M. 
CRIBRILINA LATICOSTULATA, new species. 
Plate 5. fig. 11. 
Description . — The zoarium incrusts shells. The zooecia are distinct, separated 
by a deep furrow and are somewhat elongated and elliptical; the frontal is quite 
convex and formed of 12 to 14 large and wide costules , separated from each other 
by 5-6 lacunae; and united at their extremities. The apertura is semicircular, 
bordered by a salient peristome bearing two spines on the distal part and a salient 
and thick mucro on the proximal part. The ovicell is hyperstomial placed on the 
distal zooecium, it is globular, salient and never closed by the operculum. Above 
each zooecium there is a small, simple, orbicular or elliptical avicularium. 
M easurements. 
Apertura 
ha— 0.05 mm. 
la— 0.08 mm. 
Zooecium 
Zs=0.36 mm. 
7s =0.26 mm. 
V aviations . — This species is quite rounded, which causes the lacunae to dis- 
appear. The mucro is quite salient and is raised in front of the orifice of the 
ovicell ; it manifestly protects the passage of the eggs. The spines are extremely 
fragile and have been observed only in two cases. 
The costules are intimately joined on the median axis. We have never ob- 
served the pores of the papillae. For these reasons we class this species provi- 
sionally in Cribrilina but we believe that the operculum does not close the ovicell. 
It is evident that the latter character is always problematic on the fossils. 
Occurrence . — Midwayan (Clayton limestone) : Brundidge, Alabama (rare). 
Holotype. — Cat. No. 63810, U.S.N.M. 
