MARYLAND GEOLOGICAL SURVEY 415 



Description. — A single imperfect discoidal zoarium probably referable 

 to this common Miocene species occurs in the Maryland bryozoa before 

 us. It is ovate in outline, the largest and smallest diameters being res- 

 pectively about 5.0 mm. and 3.5 mm. Concave under-surface marked by 

 irregular impressed radial lines with the surface between them granulose. 

 Convex surface celluliferous, the zooecial arrangement rather obviously 

 radial, though here and there an approach to the quincuncial arrange- 

 ment, that is more apparent than the radial in typical specimens of the 

 species, is perceptible. The zooecial covers are gone, but remains of them 

 occur in nearly all the cells as two or three blunt spines on each side of 

 the aperture. Vibracular cell situated between the ends of the zooecial 

 apertures, large, sometimes attaining a length nearly half that of a 

 zooecium, usually rounded, though often with one side less curved than 

 the other and sometimes nearly straight. The latter are oblong and vary 

 between subquadrate and ol^scurely hexagonal. Four and a half to five 

 occur in one of the radial rows in 2.0 mm. Walls thick, obtusely ridged. 

 Where the exterior portion of the zocecia is removed the inner part is 

 seen to be thin walled and each zooecium rounded rhomboidal in shape, 

 while their arrangement here is decidedly quincuncial. 



We cannot agree with Pergens ' in placing Conrad's Lunulites denticu- 

 lata as a synonym under Ciipularia vmhcUata (Def ranee). Its zooecial 

 apertures are always more hexagonal than rhomboidal, causing the radial 

 arrangement to be more pronounced, while the walls are thicker. 



Occurrence. — St. Mary's Formation. St. Mary's Eiver. 



Collection. — Maryland Geological Survey. 



Family MICROPORELLID.^. 



Genus MICROPORHLLA Hincks. 

 MiCROPORELLA PR.ECILIATA n. sp. 



Plate ex. Fig. G ; Plate CXIII, Fig. 3. 



Description. — Zoarium adnate, forming patches of two or three centi- 

 meters in diameter, composed, so far as observed, of but a single layer. 

 Zocecia subrhomboidal or hexagonal, the average length and breadth 



•Pliocane Bryozoen von Rhodos, Ann. K. K. Nat. Hofm., Bd. ii, p. 30, 1887. 



