264 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



lunar, transverse; there is not a complete polypide tube; the polypidian convexity 

 is prominent; the two opesiules are rounded, asymmetrical, rather distinct. The B 

 zooecia are of greater size and much enlarged in their distal part; the polypide 

 tube is median, quite prominent, complete; the opesiules are large, rounded or linear 

 nearly alike ; the oral arch is single or double and salient ; the distal niche is large, 

 of slight depth, and smooth. 



[^0=0.05-0.10 mm. I 5 = 0.50 mm. 



Measurements. Opesmm<, nnA a zooecmm ' OA 



[(0=0.20 mm. U?=0.30-0.36 mm. 



(-7,3=0.70-0.80 mm. 

 B zooecmm { , 



I ?s=0.34mm. 



Variations. The micrometric dimensions are extraordinarily variable. The 

 B zooecia attain a length of 1.10 mm. in the specimens from the vicinity of Bain- 

 bridge, Georgia ; they always engender two new rows of zooecia. 



The partition of the a zooecia is very oblique and begins at one of the upper 

 distal angles (fig. 5). It becomes very visible after rubbing away the zoarial sur- 

 face. The polypide slips between this partition and the opesiule in order to emerge 

 from the polypidian convexity. 



The polypide tube of the B zooecia is median, straight (see fig. 4, w), or 

 curved nearly at a right angle. The contortions of the polypide in order to emerge 

 from the zooecium (<), are really considerable (fig. 4) ; we are in ignorance regard- 

 ing the use of this complicated structure; the embryos developed at the base of the 

 distal chamber are not the cause of it. 



One of the zoaria before us covers 5 square centimeters of surface. 



Affinities. This species differs from Steganopordla jacksonica in its incrusting 

 zoarium, in its a zooecia, which are shorter, and its nonperforatecl cryptocyst. 



It is distinguished from Strganoporella (LepraUa) firm a Reuss, 1867. by its B 

 zooecia, which are much larger. 



Occurrence. Upper Jacksonian (Ocala limestone) : Chipola River, cast of 

 Marianna, Jackson County, Florida (common) : West bank of Sepulga River, 

 Escambia County, Alabama (very rare) ; 4 miles below Bainbridge. Georgia (very 

 rare) ; Old Factory, H miles above Bainbridge. Georgia (very rare). 



Middle Jacksonian : 17 miles northeast of Hawkinsville, Georgia. 



Cotypes.C&t. Nos. 64007-64009, TJ.S.N.M. 



STEGANOPORELLA VICKSBURGICA, new species. 



Plate 84, figs. 1-7. 



Description. The zoarium is formed of two lamellae placed back to back and 

 easily separable. The a zooecia are large, distinct, elongate, without distal niche; 

 the mural rim is thin and salient; the cryptocyst is deep and perforated with very 

 small pores; the opesium semilunar, transverse; the polypide tube is complete but 

 very little prominent, and the opesiules are hardly visible. The B zooecia are larger 

 and have a deep, smooth distal niche; the polypide tube is large and very promi- 



