386 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



Occurrence. Vicksburgian (".Chimney rock " of Marianna limestone) : One 

 mile north of Monroeville, Alabama (very common). 



Vicksburgian (Red Bluff clay) : Seven and one-half miles southwest from 

 Bladen Springs, Alabama (common). 



Cotypes.C&t. No. 64273, U.S.N.M. 



Group 2. ZOARITJM TJNILAMELLAR (Semieschara). 

 HIPPOMENELLA ALIFERA, new species. 



Plate 50, figs. 9-18. 



Description. The zoarium is unilamellar and creeps over algae. On the inner 

 face in contact with the substratum the zooecia are convex, hexagonal, formed of 

 an olocyst covered by a pleurocyst and often ornamented by hydrostatic tuberosi- 

 ties. The zooecia are elongated, distinct, hexagonal or oval ; the frontal is convex, 

 smooth, surrounded by two or three rows of small and numerous areolae. The 

 aperture is elliptical, elongated; the peristome very little salient, bears six large 

 spines; two small cardelles separate a large anter from a smaller poster. The 

 ovicell very large, very prominent, globular, and smooth, is hyperstomial and little 

 embedded in the distal zooecia : a small median nerve separates the two areas. The 

 avicularia are very large and salient : they are placed below and close to the aper- 

 ture; their beak is triangular and directed obliquely toward the bottom; they have a 

 calcareous pivot. 



|A.a=0.18-0.20mm. . [7^=0.70-0.80 mm. 



Measurements. Aperture , ni Zooecia 7 _ .,. _ . 



[7(7=0.14 0.16mm. 162=0.40-0.60 mm. 



Variations. This species represents the height of polymorphism; there is not 

 a single specimen comparable with another and not a single zooecium resembles its 

 neighbor. 



The areolae are often disposed in two or three rows (figs. 10, 13). sometimes 

 spreading over all the frontal (fig. 11) and becoming true tremopores. The avicu- 

 laria may be short and unsymmetrically disposed (fig. 10), but are generally very 

 large and very salient, like extended wings (figs. 11, 14). The ovicells, globular 

 (fig. 13) or pyriform (fig. 11), are almost always smooth. 



The lower face of the zoarium is smooth (fig. 15) ; each dorsal is formed of 

 two separable calcareous layers (fig. 16), a pleurocyst on an integral olocyst; the 

 hydrostatic tuberosities are rare but may become very large (fig. 17). The zoa- 

 rium may be incrusting. 



In the interior the apertura shows a porta larger than the vanna, separated 

 by two cardelles (fig. 8). 



Affinities. Its smooth ovicells and large avicularia characterize this species 

 rather well. It differs from Hippomenella radicata in its larger aperture, its 

 smooth ovicell, it avicularia symmetrically disposed, and in its dorsal not regularly 

 perforated. 



It differs from HippomeneUa transversata in its elongated aperture (and not 

 transverse) , in its more salient avicularia and more than two rows of lateral areolae. 



