BRYOZOA—CHILOSTOMATA. 169 



membranous ; the two layers of cells separate readily along the 

 median line. Cret.-Recent. 



170. B. torta Gabb and Horn. (Fig. 217, e.) Cret.-Tert. 

 Small, of compressed branches, usually twisted ; cellules in 



longitudinal lines, usually in quincunx; close together; aperture 

 oval, about half of the cell surface, without lips or peristomes; 

 colony increases in width by interpolation of new rows of cells. 

 Rancocas of New Jersey and Aquia of Maryland. 



CIV. Onychocella Waters. 

 Encrusting or erect, branches compressed, zocecia hexagonal 

 with raised margins (unless worn), oral openings semilunar or 

 crescentic ; scattered avicularian openings in pearshaped areas. 

 Cret.-Recent. 



171. 0. digitata Morton. (Fig. 217,/.) Cret.-Tert. 

 Branches compressed, acutely elliptical, bifurcating, somewhat 



twisted, 2.5-3.0 mm. wide. Zocecia bounded by a slightly 

 impressed line, apertures in front of center. Small subcircular 

 cells (avicularia) on margins and below bifurcation. 



Upper Cretacic (Rancocas) of New Jersey, Aquia of Maryland. 



CV. Membranipora Blainville. 

 Encrusting, irregular calcareous or subcalcareous expansions ; 

 zocecia irregularly arranged or in rows, with variously shaped 

 apertures according to the degree of calcification of the front wall of 

 the zocecium. Cret.-Recent. 



172. M. plebeia Gabb and Horn. Cretacic. 

 Encrusting, sometimes on 0. digitata, cells generally in radiating 



lines, elongate to pyrilorm, separated by depressed lines ; apertures 

 large ; oral openings occupying the whole cellule. 

 Rancocas of New Jersey. 



173. M. abortiva Gabb and Horn. Cretacic. 

 Cells elongate pyriform to suboval, irregularly arranged ; aper- 

 ture occupying about half the cellule, nearly terminal often acum- 

 inate in front and wide behind. 



Common in the Upper Cretacic of Timber Creek, and near 

 Mullica Hill, N.J. 



174. M. oblongula Ulrich. (Fig. 217, g.J Miocenic. 

 Zooecial apertures in longitudinal series elongate ovate to sub- 

 quadrate, about twice as long as wide, occupying entire cellule; 



