MARYLAND GEOLOGICAL SURVEY 417 



MiCROPORELLA ( ?) BIFOLIATA n. Sp. 



Plate CXIII, Figs. 6, 7, 8. 



Description. — Zoarium erect, bifoliate, not known to branch. Zooecia 

 subqnadrate or hexagonal, arranged in regular longitudinal and diagon- 

 ally intersecting series, four longitudinally and five diagonally in 2.0 

 mm. Appearance of surface varying greatly with age. In young ex- 

 amples the zooecia are more or less convex and separated, especially trans- 

 versely, by an impressed line containing one or more rows of pores ; the 

 orifice is somewhat transverse and subovate with the proximal side 

 straightened, the peristome but little elevated, the front sparsely punc- 

 tated, the avicularia, of which there is usually one to each zooecium placed 

 some distance beneath and to one side of the orifice, rather large, sub- 

 circular and divided into two nearly equal parts by a thin partition. 

 In old examples the oral part is sunken and the rest of the surface 

 abundantly punctate, while the avicularia have been somewhat reduced 

 in size. Immediately behind the orifice there is always a small ( ? peri- 

 stomial) pore. Ovicells large, rather strongly convex, punctate. 



We know of no satisfactorily classified species that may be regarded 

 as closely related to the form under consideration, and there is there- 

 fore some doubt as to its generic position. Possibly it would have heen 

 nearer the truth to call it a Porina. 



Occurrence. — Choptank Formation. Cordova. 



Collections. — Maryland Geological Survey, U. S. National Museum. 



Genus ADEONELLOPSIS Macgilliviay. 

 Adeonellopsis umbilicata (Lonsdale). 



Plate CXIII, Figs. 4, 5; Plate CXIV, Fig. 5. 



Vellepora umbilicata Lonsdale, 1845, Quar. Jour. Geol. Soc. London, voL i, p. 507. 

 Reptocelleporaria umbilicata d'Orbignj', 1851, Pal. France, vol. v, p. 423. 

 MuUiporina umbilicata Gabb and Horn, 1863, Jour. Acad. Nat. Sci. Phila., 2nd ser., 

 vol. V, p. 145, tig. 27. 



Description. — Zoarium forming irregular nodose masses, composed 

 of numerous layers, growing over foreign bodies. Zooecia of succes- 

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