XOKTH AMF.KIc AX KAIMA TEKTIAKY BKYOZOA. 491 



Affinities. This species differs t'rnni I'rill<i abdifa in its distinct x.ooeria and 

 in its /.oariiim creeping over algae and not bihunellar. 



In its exterior aspect and in the nature of its zoarium it may bo easily con- 

 founded with <'i/c1if(>pi>i-ii xj>/)i/!ujix!x I)e (iregorio, 1882. It differs from it in the 

 regular and constant presence of the median avicularium. 



Occur n ni'i -. Vicksburgian (Marianna limestone) : West Bank Conecuh River, 

 Escambia County. Alabama (common) : Murder Creek, east of Castlebury, Conecuh 

 County, Alabama (common) ; Claiborne, Monroe County, Alabama (common): 



.^i\t. Xo. (5430s. r.s.x.M. 



PORELLA CYLINDRICA. new species. 



Plate 04. tiss. 14-17. 



Description. The zoarium is free, <'i//in<lr/<'<il, bifurcated, formed by four 

 to six longitudinal rows of zooecia. The zooecia are distinct, elongated, separated 

 by a salient thread; the frontal is somewhat convex and is formed of a thick trenio- 

 cyst with large tubules. The apertura is deep and partially hidden by the median 

 avicularium: it has no peristome. The jnedian avicularium is enormous, very 

 salient, very straight with an orifice turned toward the side of the apertura. 



\lm='. \\n\\. . [2 = 0.80 mm. 



Mciixin-i mi'iifs. Apertura , /ooccia 7 



[la=0.ll mm. I fe=0.40mm. 



Affinities;. The vincularian form of its zoarium clearly distinguishes this 

 species from the species with large median avicularium, such as Porella denti- 

 culifera, Porcllit jacksonica, Porelln /unit/ens, and Porella unguiculata. 



Occam n< ,. Vicksburgian ("Chimney rock" of Marianna limestone): One 

 mile north of Monroeville. Alabama (common). 



Cof>/i><'x.t\\t. Xo. 04304, F.S.X.M. 



PORELLA ERECTA. new species. 



Pliiti- '.I-. iif;s. 17-20. 



Dexcrljifiun. The zoarium is free, bilamellar, formed of two lamellae, back 

 to back, and inseparable: the fronds arc narrow and bifurcated. 



The zooecia are distinct, long, tubular; the frontal is convex and formed 

 of a tubular tremocyst placed on a thin oloeyst with small pores. The apertura 

 is semilunar. oblique, buried, by the umbo when the latter is entire; it has no 

 peristome. The ovicell is globular, salient, with a finely porous area ; it is hyper- 

 stomial and opens into the peristomie. The median avicularium forms a very salient 

 umbo little oblique above the aperture, almost erect, very thin, and very fragile at 

 the extremity. 



\kpe=0.1f> mm. Apertura thaO.OS mm. 



llpe=tU(]mm (interior) U=0.10 mm. 



[.3=0.70 mm. 

 Zooecia< 7 



