NORTH AMERICAN EARLY TERTIARY BRYOZOA. 715 



Variations. A large number of specimens present in their inferior part two 

 inexplicable fractures, always almost identically arranged and of the same size. 

 We have figured them on plate 124. 



Affinities. The aspect of this species is similar to that of Plagioecia kirta, but 

 differs from it in its tubes bent up a little (and not rectilinear), and more widely 

 spaced in every sense. 



Occurrence. Middle Jacksonian (Castle Hayne limestone) : Wilmington, 

 North Carolina (rare). 



Upper Jacksonian (Ocala limestone) : Nine miles north of Ocala, Florida 

 (very rare); Chipola River, east of Marianna, Jackson County, Florida (rare). 



Holotype.G&t. No. 65304, U.S.N.M. 



PLAGIOECIA HIRTA, new species. 



Plate 124, figs. 3-11. 



Description. The zoarium incrusts shells and bryozoa; it is flabelliform, 

 orbicular, rarely linear. The tubes are distinct, rectilinear, hornshaped, narrowed 

 at the back, very slightly striated, arranged in regular quincunx, prolonged into a 

 very oblique peristomie; the peristome is elliptical, horizontal, very thin, often 

 sharply pointed distally. The ovicell is short, elliptical, not arched, placed near 

 the zoarial margins. There is no visible zone of growth. 



Diameter of the peristome 0.10 mm. 



Measurements. 



Distance between the peristomes__- 0.40 (0.30-0.60 mm.) 



Separation of the peristomes 0.40 mm. 



Length of the peristomie 0.20 mm. 



Variations. This species is very well characterized by its rectilinear, salient 

 tubes which give a bristling aspect to the zoarium. The zoarium, however, is rather 

 variable, but it remains quite orbicular when the substratum is flat. We figure 

 (fig. 3) a curious case of the influence of the substratum on the ovicell; in conse- 

 quence of the zoarial envelopment about a thin bryozoan, the ovicell appears 

 elongate by perspective and not transverse. It is not rare to encounter many 

 zoaria side by side, but each is provided with a distinct ancestrula. Following 

 observations already made, these zoaria do not grow over each other. 



We have seen that in the Stomatoporoids the branches of the same zoarium 

 never grow over each other; the same phenomenon occurs also in the Berenicea 

 forms. In the latter the zoarial superpositions are produced by rejuvenescence. 

 How can these animals, growing on the same substratum but proceeding from 

 different larvae, recognize each other in order not to overlap? The life of these 

 small beings is as mysterious as marvelous. 



Affinities. In its zoarial aspect and the bristling arrangement of the tubes, 

 this species has given resemblance to Berenicea verrucosa Milne-Edwards, 1838 ; it 

 differs from it in its smaller peristome (0.10 and not 0.16 mm.), its smaller zooecial 



