Gexeka of the XoRTir American Palaeozoic Bryozoa. 5i5 



ing one; base of each segment obconical; terete above and 

 strongly striated, gradually becoming flattened and cell uliferous; 

 apertures in rows separated by ridges ; central ranges of aper- 

 tures the smaller ; apertures with comparatively prominent 

 lunaria. 



DicRANOPORA, Ulrich. 



(Jour. Gin. Soc. Nat. Hist., Yol. Y, p. 166, pis. 6, 7.) 



Type, Dicranopora internodia^ Ulrich. 



Zoarium comprised of bifurcating segments; bifurcations 

 short; extremities truncate; a bifurcating segment arising from 

 each preceding truncated extremity; margins subparallel; cell 

 apertures usually arranged in parallel longitudinal rows, sepa- 

 rated by ridges ; the apertures of the outer rows being larger 

 than the others; margins of segments noncelluliferous. 



This genus bears some resemblance to Aorogenia, but differs 

 from that genus in the fact that each two segments proceed from 

 the bifurcations of the preceding segment instead of from the 

 truncated extremity of a simple segment. 



GoNioTRYPA, Ulrich. 



(Micro. Pal. of Ganada, PL 2, p. 14 ; PL 9. 1889.) 



Type, Goniotrypa hilateralis^ Ulrich. 



" Like Dicranopora in all respects, save that there is a promi- 

 nent liiedian ridge on each of the two faces of the double-leaved 

 segment." (Ulrich). • 



Family Thamnotrypidae. 



This family includes at present only the genus Thamnotrypa, a 

 form which can not well be included in any of the existing 

 families. 



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