SECONDARY AND TERTIARY FORMATIONS OF NORTH AMERICA. 157 



the other rows arising at all angles from a right angle to almost parallel, will at once 

 distinguish this pretty and unique form. 



PYRIPORA, d'Orb. 1817. 



Colony encrusting, composed of pyriform cellules placed in longitudinal and lateral 

 rows, always separated by a more or less extended pedicle, and never in contact late- 

 rally. Cellules arising by a narrow or filiform pedicle, from the front or sides of pre- 

 ceding ones. Shape usually pyriform or fusiform. Opening large and occupying the 

 greater part of the anterior portion of the cellule. Distinguished from Hippothoa by 

 the size of the opening, -which in the living state is closed by a membranous operculum. 



P. irregularis, G. and H., fig. 40. 



Hippothoa, id., G. and II., Proc. Acad. 1S60, p. 366. Id. G. and H., Jour. Acad. 

 2d ser. vol. 4, p. 400, pi. 69, f. 18—20. 



Colony encrusting, composed of robust pyriform cellules, branching longitudinally 

 and at various angles, both from the ends and sides of preceding cellules, sometimes 

 simultaneously. Cellules broadly pyriform. pedicle short and robust, widening rapidly, 

 so as occasionally to make the cellule almost elliptical. Mouth large, elliptical, ante- 

 rior, not terminal, and with its edge all in the same plane, sometimes bordered poste- 

 riorly by a slightly elevated lip, not thickened. Walls thin and without any orna- 

 mentation. 



This species resembles remotely, in the shape of its cellules, the Hippothoa simplex, 

 d'Orb., but is proportionately not half so long, and the large oval aperture places it in 

 a separate genus. We have had the opportunity of examining a large number of 

 specimens, and find it very often encrusting Eschara- digitdta. Colonies seldom show 

 more than twenty or thirty cellules, and a dozen is much nearer the usual number. 



From the Cretaceous of Timber Creek, N. J., and near Mullica Hill. 



MEMBRANIPORA, Blainv. 1S34. 



Colony testaceous, encrusting, composed of a single layer of cellules. Cellules jux- 

 taposed ; opening occupying the greater part of the cellules, closed by a membrane 

 pierced by the mouth in the living state. Ovarian vesicles not uncommon, usually 

 small. 



M. abortiva, n. s., fig. 41. — Colony encrusting. Composed of cells of an elongated 

 pyriform to a suboval shape, arranged irregularly. Cells rounded to acuminate ante- 

 riorly, sometimes elongated posteriorly, occasionally truncated. Aperture occup}-ing 

 about half the cellule ; nearly terminal, often acuminate in advance and wide behind, 

 at other times nearly elliptical. 



In some instances we have observed it constricted, almost to obliteration by a 



