Gexeka of the Xorth American Palaeozoic Bryozoa. 553 



Tkopiddpora, Hall. 

 (Report of N. Y. State Geologist for 1886, Expl. pi. 25. 1886.) 



Type, Tropidopora nana, Hall. 



(Plate 16, figs. 1,2.) 



Zoarium minute, ramose; cell apertures arranged in irregular 

 longitudinal rovvs, separated by sinuous ridges; peristomes very 

 thin, slightly elevated. 



It has been impossible to determine the internal character of 



this genus, but the external characters are so different from other 



Trematoporoid forms, that there here seems a necessity for a new 



genus. 



Family Bactroporidae. 



Baotkopora, Hall. 

 (Pal. N. Y., Yol. YI, p. 19;^. 1887.) 

 Type, Baetropora granistriata, Hall. 



(Plate 16, figs, 13, 14.) 

 Zoarium simple, unbranched, lower extremity pointed, striated; 

 external and internal characters very similar to Rhombopoka, 

 but it can not be placed in the family RnoMBOPORioiE, on account 

 of its simple form and pointed, striated base. 



JSematopora., Ulrich. 

 (Geol. Sur. 111., Yol. YIII, p. 401. 1890.) 

 Type, N'ematopora quadrata, Ulrich. 



" Zoarium ramose, very slender ; continuous above the pointed 

 basal extremity; cells subtubular, short; arranged in a radial 



Fig. ItZ. Xematopora quadrata, natural size and xlS. 

 Fig. 12:3. A vertical section, xl8. 



Fig. 124. . X. delicatula. A frond, natural size and xl8. 

 Fig. 12.5. A transverse section, x50. 



70 



