Genera of the I^orth American Palaeozoic Bryozoa. 539 



apertures directed toward the distal margin of the expansion; 

 lunarium moderate or obsolete ; cell tubes oblique, the anterior 

 walls thinned and flexuous ; diaphragms numerous, often 

 recurved ; ooecium a large oval cell, showing a convex space with 

 a small apical perforation." (Ulrich.) 



• Phractopora, Hall. 

 (Trans. Albany Inst., abstract, p. 12. 1881.) 

 Glyptotrypa^ Ulrich. 

 Type, Phractopora cristata^ Hall. 



(Plate 34, figs. 11-14.) 



Zoarium consisting of explanate fronds, having the surface 

 raised at irregular intervals into prominent crests, which are 

 cellulif erous on each face ; cells tubular, arising from a mesotheca, 

 celluJiferous on each face, with lunaria, which are frequently 

 indistinct. The apertures are generally disposed in diagonally 

 intersecting rows ; intercellular structure, near the base, irreg- 

 ularly vesiculose, and having the appearance of septate tubuli 

 above. 



Fig. 95. Phractopora sagenella, natural size. 

 Fig. 96. Phractopora michelini, natural size. 



