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 very oblique, almost transverse, 

 large (Lav 0.25 mm.), quite pointed, provided with a calcareous pivot, and directed 

 toward the interior of the aperture. 



[Aa=0.13mm. 



Measurements. Aperture \ , _ 1 _ 



Urt=0.l5 mm. 



[7,3=0.55-0.60 mm. 

 , _ . ,. ,. .... 



l/3=0.4o 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 If cic/otum 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 

 Figularifi. 



In its smooth ovicell it differs from Gephyrotes convexa and from G. spectalnlis. 



Occurrence. Midwayan (Clayton limestone) : Luverne, Crenshaw County, 

 Alabama (rare). 



s.Crt. No. 63814, U.S.N.M. 



GEPHYROTES CONVEXA, new species. 



Plate 42, figs. 2. 3. 



Description. -The zoarium incrus'ts Orbitoide?. 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 zqoecia 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. 



lha=0.08 . . fZs=0.52-0.60mm. 



Measurements.-A.pert ffc =0 . l(WU2 mm . Zooecia { 7 ,,=0.40-0.4fi mm. 



