214 SYSTEMATIC PALEONTOLOGY 



radiating lines; elongate, acuminate anteriorly, broadly truncate behind. 

 Opening subtriangular, with the sides convex, often approaching an oval 

 in very long cellules. Surface regularly convex, bordered anteriorly and 

 laterally by a slightly elevated, rounded edge, usually becoming obsolete 

 as it approaches the proximal end of the cellule. Special pore placed 

 in advance of the opening, small and round. No ovarian vesicles were 

 observed. Old cellules are closed over by a continuation of the surface 

 wall totally obliterating the aperture. In this case the ' special pore ' 

 is also generally obliterated, merely showing a slight depression." Gabb 

 and Horn, 1862. 



The Eocene specimens are coarser in appearance than the Cretaceous 

 form of the species, of which the writer has a number of excellent 

 examples. They differ further in the more pronounced character of the 

 granulation of the front wall and opesial margin, the Cretaceous form 

 being almost smooth; in more frequently assuming a rhomboidal form 

 of zooecium; and in the relatively smaller size of the opesium and larger 

 avicularia. Cucullate ooecia, less prominent but otherwise similar to 

 those of Me7nl)ranipora spiculosa, occur not infrequently upon the Cre- 

 taceous specimens but are wanting on the Eocene material in hand. 

 When these occur they take the place of the avicularium which other- 

 wise occurs invariably on, or, Just above, the upper rim of the zooecium. 



The species occurs in the Cretaceous at Mullica Hill, Timber Creek, 

 and Vincentown, N. J. 



Membranipora spiculosa is a closely related species, but has a more 

 ovate and larger opesiUm and differently shaped zooecia. 



Occurrence. — Aquia FoEMATioisr. Upper Marlboro. 



Collection. — Maryland Geological Survey. 



Genus BIFLUSTRA d'Oibigny. 



BiFLUSTKA TORTA Gabb and Horn. 



Plate LX, Fig. 7. 



BifluKira torta Gabb and Horn, 1863, Jour. Acad. Nat. Sci. Phila., 3ud ser., voL v, 

 p. 152, pi. XX, tig. 36. 



Description. — " Colony composed of very compressed branches, usu- 

 ally twisted, rarely in the same plane for more than a quarter of an 



