Geneea of the Korth American Palaeozoic Bryozoa. 507 



parallel rows, separated by a carina, the caringe of the primary 

 branches being much more prominent than those of the second- 

 ary branches. 



Ptilopobina, Hall. 

 (Pal. K Y., Yol. YI, p. 172, PL 43, figs. 7-9.) 

 Type, Ptilojporiiia sinistralis, Hall. 



(Plate 4, figs. 8-12.) • 

 Bryozoum having the same manner of growth and general 

 appearance as Ptiloporslla, but differing from that genus in 

 having three or more ranges of cell apertures, not separated by a 

 carina. This genus bears the same relation to Ptiloporella that 

 PoLTPOBA does to Fenestella. 



PiNNAPORiNA, Simpson. 

 (Ann. Kept, of K Y. State Geologist for 1893. 1894.) 

 Type, Pinnaporina pinnata, Hall (sp.), 



(Plate 4, fig. 7.) 

 In general appearance and disposition of cell apertures this 

 genus resembles Ptiloporina, but differs from that genus in hav- 

 ing a fl^ibellate mode of growth. It differs from Pinnaporella 

 in having three or more ranges of cell apertures not separated 

 by a carina. 



Hemitrtpa, Phillips. 

 (Pal. Foss. Cornwall, Devon, and West Somerset, p. 27, 1841.) 



Type, Jlemitrypa oculata^ Phillips. 



(Plate 5, figs. 1-11.) 



Bryozoum having the same general appearance and manner of 

 growth as FE-'fESTELLA ; cell apertures arranged in two parallel 

 rows separated by a carina ; carina prominent, expanded above 

 and having lateral processes (scalas), which, meeting midway 

 between the carinse. form an intermediate ridge or pseudocarina. 

 The spaces between the scalae or fenestrules usually correspond 

 in number to the cell apertures. 



This form differs from Unitrtpa in having simple lateral pro- 

 jections, instead of thin oblique plates, and in thejormation of a 

 pseudocarina. 



