Genera of the ^N'orth American Palaeozoic Bryozoa. 503 



''Dissepi^nents short, strong and enlarged at their junction with 

 the longitudinal rays. 



'^Fenestrules^ ^ong^ oval, or elliptical, rarely quadrangular, two 

 to two and a half in two lines measured longitudinally ; four in 

 two lines transversely. 



'^ Cells in two rows on either side of the midrib, most generally 

 opposite to the two rows, and opposite on the two sides of the 

 midrib, five to each fenestrule, or twenty inclusive of the two 

 rows on either side. 



^^ Reverse^ fenestrules quadrangular from the want of expansion 

 in the junction of the dissepiments; rays and dissepiments 

 rounded, minutely tubular, striate." 



This species differs from Fenestella in its flabellate mode of 

 growth, and in having two rows of cell apertures on each side 

 of a median carina. It differs from Flabelliporina, in having a 

 median keel and it having uniformly four rows of cell apertures. 



Fig. 42. Fenestralia St. Ludovici. Frond natural size. 



Fig. 43. A portion enlarged. 



Eeteporella, Simpson. 

 (Ann. Kept, of State Geologist of N. Y. for 1893.) 

 Type, Reteporella undulata. 



(Plate 1, figs. 1-5.) 

 Bryozoum consisting of infundibuliform or cup-shaped expan- 

 sions, celluliferous on one face only ; branches sinuous or zig-zag, 



