302 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
a small cribriform area formed of three or four pairs of costules, without lateral 
median lacunae. Many zooecia bear a spiramen. The aperture is elliptical, trans- 
verse, provided with a vestibular arch, and surrounded by a very salient peristome. 
The ovicell, embedded in the distal zooecium, is large, globular, improminent; it 
opens into a false peristome in front of the spiramen : it is closed by the operculum 
when the latter is open. The oral avicularia are A^ery oblique, almost transverse, 
large (Lav 0.25 mm.), quite pointed, provided with a calcareous pivot, and directed 
toward the interior of the aperture. 
M easurements . — Aperture 
f ha= 0.13 mm. 
i/«=0.15 mm. 
Zooecia 
f Lz= 0.55-0.60 mm. 
1 / 3 = 0.45 mm. (including avicularia). 
Variations and affinities . — The spiramen is present on all the zooecia and is 
situated at the distal extremity of the cribriform area, nearly perpendicularly to 
the plane of the zooecia. It is necessary to incline the specimen preparation in 
order to see it clearly, and in our figures it has disappeared because of perspective. 
This species differs from Gephyrotes levigatum in its very prominent peristome 
and its large avicularia (Lav 0.25 mm. and not 0.15 mm.). Like that species, it 
shows such undoubted resemblances with Membraniporella that further examination 
of numerous specimens is required. On the other hand, the presence of a spiramen 
seems to indicate that there is a compensatrix buried under the costules, as in 
Figularia. 
In its smooth ovicell it differs from Gephyrotes convexa and from G. speetabilis. 
Occurrence . — Midwayan (Clayton limestone) : Luverne, Crenshaw County, 
Alabama (rare). 
Cotypes. — Cat. No. 63814, U.S.N.M. 
GEPHYROTES CONVEXA, new species. 
Plate 42, figs. 2, 3. 
Description . — The zoarium incrusts Orbitoides. The zooecia are distinct, sepa- 
rated by a deep furrow, elongated, elliptical, distended; the frontal is very convex 
and consists of a small gymnocyst surrounding a cribriform area; this area is formed 
of six or seven pairs of thick costules closely united and decorated with at least two 
quite prominent lumen pores. The aperture is semilunar, transverse; the proximal 
border is somewhat concave, and the distal border bears four hollow spines. The 
ovarian zooecia alone bear the ovicell, the spiramen, and the oral avicularia. The 
ovicell is hyperstomial and little distinct, convex, transverse, bordered in front; 
it opens into the peristomie formed by the avicularia and the lamella which bears 
the spiramen; it is closed by the operculum at the moment the latter is opened. 
The two avicularia are very prominent, triangular, the point toward the proximal 
border of the aperture. The spiramen opens above the aperture. No dietellae. 
JAa=0.08 . „ • \Lz— 0.52-0.60 mm. 
Measurements. Aperture { fa=al0 _ al2 mm . Zooecl! '1fe=0.40-0.4fi mm . 
