BRYOZOA. 



391 



commonly lanceolate or falciform, sometimes a broad undulat- 

 ing expansion, at other times dichotomously branched with the 

 margins parallel. Proximal extremity longitudinally striated, 

 pointed or wedge-shaped. Lateral margins of frond acute, non- 

 celluliferous, smooth or obliquely striated. Small monticules 

 usually present in the large species. Zocecia with subcircular or 

 elliptical superficial apertures, surrounded by a sloping area of 

 quadrate, rhombic or hexagonal outline. Apertures arranged 

 in a plumose manner, with longitudinal series in the center and, 

 diverging from these on each side, oblique lateral rows; or 

 simply in regular diagonally intersecting series. Both hemisepta 

 usually well developed. 



Type: P. lanceolata Goldf. Range, Trenton to Upper Helder- 

 berg. 



F:^. 11. Sections of Ptilodictya. All the figures are magnified x25. a. Portion of a 

 vertical section of Ptilodictya magnified S. A. Miller, showing several zooecia with hemi- 

 septa ; b, b', and b". three portions of a tangential section of same, showing structure of 

 zoarium at various depths below rhe surface :c, zooecium of same sectioned just be- 

 neath the aperture, and showing slightly different structure from what is seen in 6." 

 d, vertical section of Ptilodictya lanceolata Goldf.. from Gotland; e. tangential section 

 of the American representative of the species; Clinton gr., Dayton, Ohio. (P. erjtanfn 

 Hall, Ind. Geol. Sur., voL 12, 1882, not Phaenopora expansa Hall and Whitfleld. Pal. Ohio, 

 voL n, 1875). 



