612 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



festlv the frontal is formed of a pleurocyst with extremely fine granules superposed 

 on the olocyst. The considerable development, attaining 0.15 mm. in length, of 

 the peristomie is very characteristic ; it seems to us that it was uniquely of pleuro- 

 cystal origin. 



Occurrence. Vicksburgian (Byram marl) : Byram, Mississippi (very rare). 



Holotype.C&t. No. 64328, U.S.N.M. 



HOLOPORELLA DISCUS, new species. 

 Plate 102, figs. 10-13. 



Description. The zoarium is free and discoidal, of 8 millimeters in diameter 

 at the most. On the lower face the zooecia are oriented, irregularly hexagonal, 

 perforated by a small submedian pore (corresponding perhaps to the radicles). 

 The superficial zooecia are erect or quite oblique, distant from one another; the 

 frontal is convex and granular, surrounded by seven or eight widely spaced areolar 

 pores. The apertura is formed of an anter almost circular and of a small, somewhat 

 concave poster, separated by two very small cardelles; the peristome is wide crenu- 

 lated; it limits an infundibuliform peristomie. The deep zooecia are deprived of 

 frontal. The incomplete zooecia are large and rare. 



Measurements. Apertura 7 " 



(la 0.13mm. 



Variations. We have supposed that the pores of the inner face are the radicles 

 which permit the zoarium to attach itself to stones or shells. The larva is fas- 

 tened on a minute fragment of bryozoa or shells and never on a large surface. The 

 absence of vibracula, that is to say, of all system of stabilization, does not allow us 

 to believe that the zoarium could attach itself to the algae or float freely below 

 their fronds in the manner of the Lunulites. 



Affinities. The affinities of this species are chiefly with Holoporella crassi- 

 collls, in which the peristomie is also infundibuliform and the dimensions very 

 close. Holoporella discus differs from it in the presence of areolae. in the absence 

 of multiple spines, and in its free, discoidal, nonincrusting zoarium. 



It differs from Schismopora orbiculata, in which the zoarium is also discoidal, 

 in the form of its apertura deprived of rimule, in its very erect zooecia and in the 

 presence of perforations on the lower face. 



Occurrence. Yncksburgian (" Chimney rock ' member of Marianna limestone) : 

 One mile north of Monroeville, Alabama (very common). 



Cotypes.Cat. No. 64330, U.S.N.M. 



HOLOPORELLA BIROSTRATA, new species. 



Plate 76, figs. 20-24. 



Description. The zoarium forms a small convex mass, incrusting stones. The 

 superficial zooecia are erect and salient; the frontal is convex, smooth, and bears 

 two or three small salient avicularia, with pivot; it is prolonged into a bifid beak. 

 which partially masks the apertura. The ovicell is hyperstomial, recumbent, salient, 



