436 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



Occurrence, Vicksburgiaii (Marianna limestone) : Salt Mountain, 5 miles 

 south of Jackson, Alabama (very rare) ; near Claiborne, Monroe County, Alabama 

 (rare) ; deep well in Escambia County, Alabama (very rare). 



Cotypes.Cat. No. 64293, U.S.N.M. 



ENOPLOSTOMELLA RHOMBOIDALIS, new species. 



Plate 90. figs. 10-16. 



Description. The zoarium is free, cylindrical, or somewhat compressed, bi- 

 furcated, formed of two lamellae, back to back, and inseparable. The zooecia are 

 little distinct, elongated, rhomboidal, separated by a prominent thread ; the frontal 

 is somewhat convex and formed by a thick tremocyst with very large tubules resting 

 on a thin olocyst irregularly perforated. The aportura is very oblique, semilunar. 

 with a proximally concave border; the peristomice is elongated, much buried, with 

 a triangular rimule-spiramen. The ovicell is hyperstomial, opening into the per- 

 istomie, little salient, globular, ornamented with large tremopores. In the peris- 

 tomie there is a small triangular avicularium with pivot, placed transversely. 



Measurements. Peristomice |Ape=0.16 mm . |Zs = 0.65-0.75 mm. 



(exterior) \lpe=0.12 mm. la Us=0.45-0.60 mm. 



Variations. The thread separating the zooecia is quite variable and changes 

 the external aspect considerably; it is thickened laterally (fig. 12) or only near 

 the apertura (fig. 14). It gives to the zooecia a greater width (fig. 13) or less 

 (fig. 15). 



In the interior, the structure is more regular, but it may be noted that the 

 small perforations of the olocyst are not regularly arranged in quincunx, an occur- 

 rence which is very rare. 



Affinities. This species differs from Enoplostomella crassimuralis, in which 

 the zoarium has some resemblance, in its rhomboidal form, its solid and not hollow 

 zoarium and its peristomice still more imbedded. 



It differs from Enoplostomella defixa, also with a cylindrical zoarium. in its 

 smaller and more hidden peristomial avicularium. its much less salient ovicell and 

 in its less zooecial width. 



Occurrence. Vicksburgian (Marianna limestone) : One mile north of Mon- 

 roeville, Alabama (rare) ; 2^ miles north of Millry, Washington County, Alabama 

 (rare). 



Cotypes. Cat. No. 64291. U.S.N.M. 



ENOPLOSTOMELLA DEFIXA Canu and Bassler, 1917. 



Plate 91, figs. 12-21. 



1917. Eiioiilostomclla deft.ra CAKU and BASSLER, Synopsis of American Early Tertiary 

 Cheilostome Bryozoa, Bulletin 96. United States National Museum, p. 40, pi. 4, fis. 8. 



Description. The zoarium is free, cylindrical, vinculariform. formed of six 

 to seven longitudinal rows of zooecia. The zooecia are indistinct; the frontal is 

 little thickened, convex, formed of a tremocyst with large pores placed above an 



