NORTH AMERICAN EARLY TERTIARY BKYOZOA. 95 



gitudinal rows generally very regular. Apertures occupying the whole of the large 

 opesium, quite regularly ovate in shape. Rim or interapertural space narrower than 

 the opesia, rounded, sometimes angular in the middle, but oftener with a depressed 

 interzooecial suture line, marked with close transverse lines or wrinkles. Taking 

 the place of an ordinary zooecium, isolated cells, or, more commonly, two or three 

 in longitudinal sequence, occur which differ from the rest in having a convex cover 

 with a narrow median slit, and above the slit a linear crescentic impression. 

 These cells may represent an unusual type of ooecia, but more probably are to be 

 considered as a form of vicarious avicularia or vibracula. 



" The specimens upon which the species is founded are divisible into two 

 varieties, one with smaller zooccia and opesia and thicker walls than the other. 

 Measuring longitudinally the former has four and one-half zooecia in 2 mm., the 

 other only three and a half. Diagonally one has six, the other h've in the same 

 space. Thickness of zoarial sheet not exceeding 0.2 mm." 



A restudy of the types shows Ulrich's description to be exact. Besides the 

 abnormal zooecia pointed out by this author we have noted certain zooecia with 

 double mural rim, these having undergone total regeneration. It is still impossible 

 to place this species generically because neither ovicell. avicularia, nor interopesial 

 cavities have been observed. The rarity of the specimens does not permit the 

 determination of the occurrence of dietcllae. 



. [7(r>=0.32 mm. . I 2 = 0.50 mm. 



Measurements. Opesia., _. /ooecia, . 



(1 o=0.2Q mm. | A* =0.30 mm. 



Occurrence. Lowest Eocene (Bryozoan bed at base of Aqiiia formation) : 

 Upper Marlboro. Maryland (very rare). 



MEMBRANIPORINA CANALIFERA. new species. 



Flute 3. figs. 0. 10. 



Description. The zoarium is incrusting shells. The zooecia are little distinct, 

 the neighboring mural rims being intimately joined together: the mural rim is 

 hollowed and contains a circular ca-nal about the opesium. which is elliptical and 

 median. 



. Opesia. 



0=0.30 mm. . 1^2=0.37-0.42 mm. 



7=0.20-0.25 mm. ' Cla |^ = 0.30-0.35 mm. 



Variations. This species is well characterized by its circular canal, the use 

 of which is unknown. Perhaps it contained glands analogous to those which 

 Waters 1 has described in Adi nifii'ii (Membranipora) armatu Haswell. 1880. In 

 the young zooecia this canal is invisible and closed. The calcified zooecia have a 

 small linear orifice. 



It is impossible to class this species generically, for neither ovicell nor intero- 

 pesial cavities have been observed. 



1 1913. Waters. Marine Fauna of British East Africa :in<l Z-mzilmr. 'I,. !i..-r..rnata. 

 Zoological Society. I.onilon, 1913, p. JM:. pi. 71. fi. !)1. 



