NORTH AMERICAN EARLY TERTIARY BRYOZOA. 583 



surrounded by a line of minute areolae: it is convex transversely and concave longi- 

 tudinally. The a pert ura is little visible exteriorly, transverse, semielliptical with 

 a proximal border slightly convex: the peristome is very little salient and bears 

 six distal spines; its proximal lip is a little salient palette more or less oblique; 

 partially hiding the apertura, and whose lateral borders are straight. The ovicell 

 is globular, smooth, salient, fixed in part on the distal zooecium: it is hyperstomial 

 and recumbent: its orifice is rarely visible exteriorly. 



,, |^ = 0.0. , 



Measurements. Apertura , 7 Zooecia 7 



(to=O.OS-0.12 mm. lfe=0.30 mm. 



T ariations. The zooecia grouped in long, linear, adjacent series, characterize 

 quite well this species (fig. 19) ; however, many zoaria have their zooecia regularly 

 disposed in quincunx (figs. 16, 17). 



The areolae are rarely visible; the aspect of the frontal is then absolutely 

 smooth. However, after brushing and washing with patience some specimens, 

 we have been able to discover the areolae: they are extremely small, but their 

 reality is not to be doubted. At the extremity of the large zoaria the zooecia are 

 rather large. 



This species may easily be recognized at first glance by the peculiar disposition 

 of its labial mucro; it has straight borders and is clearly detached on the wider 

 apertura, which appears thus ornamented laterally with two sorts of linear or 

 circular opesiules. 



In the interior the olocyst presents some kinds of fibers radiating from the 

 apertura (fig. 18). 



On one specimen we have observed a membraniporoid ancestrula. 



Affiniti 's. In its smooth zooecia it resembles flemicyc7v/>ii/ii />i//'iijini<-t(t; it 

 differs from it in its smaller zooecia (Zs=0.30 and not 0.50 mm.), never longi- 

 tudinally concave, in larger labial mucro, and in being bordered by false opesiules. 



It differs from Perigastrella depressa in its smaller zooecia (Zs=0.40 and not 

 0.50 mm.), in the presence of a labial mucro. and in its much more convex frontal. 



Occurrence. Lower Jacksonian (Moodys marl) : Jackson, Mississippi (rare). 



Middle Jacksonian: Wilmington. North Carolina (common). 



Vicksburgian (Marianna limestone) : Salt Mountain, 5 miles south of Jack- 

 son, Alabama (rare) : 1 mile north of Monroeville, Alabama (rare). 



Cott/pes.Cnt. Nos. 64202, 64203. U.S.X.M. 



PERIGASTRELLA PLANA, new species. 



Plate 100, figs. 18-21. 



Description. The zoarium incrusts shells. The zooecia are distinct, elongated, 

 rather large, oval; the frontal is almost flat, bordered by a double row of small 

 prominent areolae and formed of a smooth or granular pleurocyst. The apertura 

 is semielliptical, transverse, with a straight, finely crenulated proximal border; 

 the peristome is complete, salient, thick; it bears six distal spines and a wide, convex. 

 salient, oblique, labial mucro. The ovicell is salient, transverse : its orifice is quite 



