220 SYSTEMATIC PALEONTOLOGY 



of the zooecia, in aged conditions especially, scarcely distinguishable and 

 mainly hy a double row of pores Avhich, as shown by fractures, are the 

 mouths of small tubes traversing the walls in a vertical direction. Front 

 wall slightly convex, perforated, the pores usually smaller than those 

 outlining the zooecia, distinctly visible on the inner surface, sometimes 

 wanting over a varying space Just behind the aperture. The latter is 

 rounded in front, nearly straight behind, with the angles rounded, gen- 

 erally semielliptical, the width and length averaging, respectively, 0.15 

 and 0.13 mm. Small, round or oval avicularia generally present. Their 

 position is variable though usually close to the rim of the aperture. 

 While an occasional zooecium may occur, having no avicularia, as many 

 or more will be found having one on each side of the aperture. Ooecia 

 unknown. 



Fractures dividing the zooecia vertically (see Fig. 18) show that the 

 walls (side and front) are traversed by minute, wavy, vertical tubuli and 

 that the zooecial cavities are connected by two series of pores, the larger 

 set near the bottom and a row of smaller pores above the midhight. 

 The openings of the larger set are often irregularly distributed over 

 the coticave floors of the zooecia. 



A fine specimen from the Cretaceous at Vincentown, IST. J., is of a 

 species closely related to L. suhplana but distinguished by several readily 

 apparent differences. In it the young zooecia are more convex than in 

 L. suhplana, and the convex portion entirely without perforations. With 

 age, however, the surface becomes distinctly pitted. The vibracula also 

 are more regularly and numerously developed, most zooecia having one 

 on each side of the aperture. The Vincentown specimens may belong 

 to Gabb and Horn's Eeptocelleporaria aspera but certain discrepancies 

 between it and their description and figure render a positive identifi- 

 cation impossible at present. 



Occurrence. — Aquia Foemation. Upper Marlboro. 



Collection. — Maryland Geological Survey. 



Lepealia labiosa n. sp. 

 Plate LX, Figs. 15, 16. 

 Description. — Zoarium forming thin crusts over shells and other for- 

 eign bodies. Zooecia rhomboidal, hexagonal or subovate, arranged more 



