Genera of the North American- Palaeozoic Bryozoa. 555 



lar, arising from the epitheca, and parallel with it for a short 

 distance, then turning abruptly outward ; apertures circular or 

 oval, sometimes irregularly disposed, at other times in a more or 

 less regular quincunx order; peristomes thin, distinctly and 

 equally elevated, usually smooth, but sometimes with numerous 

 minute nodes or spinules ; intercellular space occupied by 

 irregularly disposed vesicles, or by regularly superimposed 

 vesicles, resembling tabulate mesopores; interapertural space 

 occupied by minute angular pits. This genus has been con- 

 sidered by one or more authors as a synonym of Chilotrypa, but 

 the structure is radically different. In that genus the cells arise 

 from a small, irregularly contracting and expanding tube, and 

 the posterior portion of the peristome is much the thickest, 

 strongly elevated and hood-like. Compare the figures of the 

 two genera. 



FisTULiPORiNii, nov. gen. 

 (Plate 21, figs. 11-15.) 



Type, Fistuliporina serrulata. 



Zoarium usually consisting of free or incrusting explanate 

 fronds, or of masses formed by the accretion of successive layers 

 of growth ; cells tubular, cylindrical, rectangular or oblique to 

 the surface ; intercellular space, near the base, occupied by 

 irregularly disposed vesicles; above by regularly superimposed 

 vesicles, or by tabulate tubuli (mesopores) ; cell apertures circu- 

 lar or oval ; irregularly disposed ; peristomes equally developed, 

 often prominent ; often granulose or spinulose ; interapertural 

 space occupied by angular pits, and frequently, in addition, by 

 more or less prominent conical nodes or spines. This genus 

 differs from Fistulipora. in the form of the cell tube, and in the 

 absence of pseudosepta and lunaria. 



PiNAooTEYPA, Ulrich. 

 (Geol. Sur. 111., Vol. YIII, p. 384. 1890.) 

 Type, Pinacotrypa elegans^ Ulrich. 



" Thin, contorted expansions, with a wrinkled epitheca below ; 

 cells with sub circular apertures, and Well-developed granose peris- 

 tomes, thin walls, and, so far as observed, no lunarium ; inter- 

 cellular spaces wide, occupied by a single series of very large 



