Genera of the Xorth Americax Palaeozoic Bryozoa. 551 



ISiKhii. t.TKYP.^, Ulrich. 



(Geol. Sur. 111., Vol. YIII, p. 103. 1890.) 

 Type, Sty^eblotryjpa NickeUi^ Ulrich. 



(Plate 19. figs. 14, 15.) 

 The internal and external characters of this genus are very 

 similar to those of Rhombopora, but between the ends of the cell 

 apertures are one or more angular pits, and in the peripheral 

 intercellular space mesopores instead of "spiniform tubuli." 



Callotrypa, Hall. 



(Pal K Y., Vol. YI, p. 2^. 1887.) 



Type, Callotrypa macrojpora^ Hall. 



(Plate 18, figs. 8-14.) 



Zoarium ramose solid; cells arising from an imaginary axis at 

 the center of the branch ; cell apertures oval, irregularly dis- 

 posed; peristomes equally elevated; interapertural space occu- 

 pied by angular pits; sometimes there are also more or less 

 prominent spines ; peripheral intercellular space occupied by 

 mesopores and spiniform tubuli. 



The internal structure of this species is almost identical with 

 SiRtBLOTRYPA, but it differs from that genus in having the cell aper- 

 tures irregularly disposed and entirely surrounded by the meso- 



pore apertures. 



Byjhopora, Miller and Dyer. 



(Cont. to Pal., ISTo. 2, p. 6. 1879.) 

 Type, Bythopora fruticosa, Miller and Dyer. 

 '•Dendroid, branches small, sometimes anastomosing ; smooth; 

 cell apertures longer than wide ; separated by impressed lines." 



120 



S^ 



"^^ 



IJL 



Fig. 119. Specimens of the genus, nat. size. 

 Fio. 120. Bythopora Herricki, surface, x9. 

 Fig. 121. B. alcicomis.'uS. 



