BRYOZOA—CYCLOSTOMATA. 



121 



17. M. mundulum Ulrich. (Fig. 178, g, h.) Ordovicic. 



Branches about half a millimeter in diameter, faintly striated trans- 

 versely, and with the tube-like zocecia projecting upward and out- 

 ward in a spiral series. 

 Trenton of Minnesota. 



XIII. Phacelopor.\ Ulrich. 



Zoarium articulated ; two or more 

 conical zocecia form cone-shaped 

 bundles, with circular slightly con- 

 tracted subterminal aperture. Ord.- 

 Sil. 



18. P. pertenuis Ulrich. (Fig. 



178, i.) Ordovicic. 



Minute, thread-like, the segments 

 in linear series, frequently double, 

 producing a dichotomous branching, 

 and each comprising a pair of zoce- 

 cia, 06 to 0.8 mm. in length. 



Richmond of Illinois. 



6 



Fig. 180. Reptaria slolonifera : 

 a, frond on Orthoceras X L '■> &> 

 portion enlarged X 6. (After Hall 

 and Simpson. ) 



XIV. Ceramopora Hall. 

 Discoidal zoaria free or attached 

 by center of base ; under surface 

 with one or more layers of small ir- 

 regular cells ; zocecia radiating from 

 depressed center on upper surface, with oblique apertures imbri- 

 cating, and short, irregular mesopores decreasing in number out- 

 ward. Siluric. 



19. C. imbricata Hall. (Fig. 181.) Siluric. 



Depressed hemispheric, flattened or convex on lower side; aper- 

 tures arched or triangular, opening on all sides toward outer mar- 

 gin, in alternate imbricating series. 



Niagara of New York, Indiana, etc. 



XV. Ceramoporella Ulrich. 



Zoarium of incrusting layers, often on other Bryozoa, with short, 

 tubular, thin-walled zocecia with oval oblique apertures, the lu- 

 narium forming a hood ; abundant mesopores. Ordovicic. 



