104 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



Description. The zoarium is Lunulites in form, slightly convex, with the inner 

 face concave. The zooecia are elongated, pyrif orm, distinct ; the mural rim is regu- 

 lar, convex, projecting distally. The opesium is pyriform, entire. The ancestrular 

 zooecia are normal or radicular. The vibracula are small, narrow, symmetrical, 

 with neither condyle nor small canal. On the inner face the disks are thinner at 

 the center; they are formed of radial costules with the zooecia in one row and per- 

 forated with a line of irregular pores. A large distal septula is present. 



Variations. This species is very constant in its zooecial form. The principal 

 variations are produced in the vicinity of the ancestrula. according to the con- 

 ditions under which the larva becomes fixed. The larva affixes itself as customary 

 on a grain of sand (figs. 11, 13, 14). There are four sorts of ancestrular zooecia. 

 1. The ancestrula gives rise to normal zooecia and a discoidal zoarium results (figs. 

 8, 11). 2. The ancestrula engenders a flabelliform zoarium of normal zooecia 

 (variety duclosii} (fig. 2). The zoarium then becomes discoidal by the especial 

 proliferation of the lateral rows. 3. The ancestrula gives rise to a discoidal 

 zoarium commencing with radicular zooecia (var. almina) (fig. 5), this zone of 

 radicular zooecia being more or less large. 4. The ancestrula gives origin to a 

 flabelliform zoarium uniquely composed of vibracula (fig. 17). The ancestrula 

 may be visible (fig. 8) or immersed (figs. 3, 5). The inner face is also quite va- 

 riable; very often the primitive flabelliform zoarium is visible (figs. 9, 10) ; again, 

 it is often covered by the accompanying disks (fig. 16). 



The disks piled up to compose the zoarium are much thinner at the center 

 (which preserves the cupuliform aspect of the zoarium) (fig. 16). Frequently 

 broken disks are found showing the construction of the genus very well (figs. 12, 

 13. 15). In vertical fractures the fibrous texture of the zoarium is quite visible 

 (fig. 14). 



Occurrence. Claibornian (Gosport sand) : Claiborne, Alabama (very abun- 

 dant) ; Gopher Hill, Tombigbee River, Alabama; 1 mile southwest of Rockville, 

 Alabama (very abundant). 



Claibornian (Cook Mountain formation) : Moseleys Ferry, Caldwell County, 

 Texas (abundant). 



Claibornian (Lisbon formation) : Wautubbee Hills, 4 miles south of Enter- 

 prise, Mississippi (rare). 



Lower Jacksonian : 3i miles southwest of Shell Bluff post office, Georgia (rare). 



Lower Jacksonian (Moodysmarl) : Jackson, Mississippi (abundant). 



Vicksburgian (Red Bluff clay) : Red Bluff, Wayne County, Mississippi (rare). 



Plesiotypes.GsA. No. 63837, IT.S.N.M. 



TROCHOPORA TRUNCATA De Gregorio, 1890. 



Plate 11, figs. 1-0. 



1S90. Lunulites (DisroflustrcUana) bond-, v.ir. tnmcata DE GREC.ORIO, Monographic de la 

 Faune Eocenique de 1'Alabauia et surtout de celle de Claiborne de 1'Etage Parisien, 

 Arinalos de Geologic et de Paleontologie, Livraisons 7, 8, p. 245, pi. 41, figs. 34-41. 



Description. The zoarium is a conical Lunulites, solid, formed of successive 

 disks. The zooecia are' hexagonal, distinct, arranged in radial and circular rows; 



