MARYLAND GEOLOGICAL SURVEY 757 



edges on the sides of the corallum do not alternate in prominence. The 

 bifurcations of the separate cycles of costae are at more irregular distances 

 from the center and the costae are thinner and more finely denticulate. In 

 M . cribraria the costaa and perforations of the base are largely obscured by 

 irregular calcification and the costae project more prominently on the 

 periphery. In M . mississippiensis the basal costae are narrower, smoother, 

 and flatter, the bifurcations of each cycle are more irregularly spaced with 

 reference to the center, and the profile of the side of the corallum is not so 

 steep and is slightly truncated. In M. rotatilis the basal costae are thinner, 

 sharper, and much smoother. In M. americana the costae are narrower 

 and sharper, and the bifurcations producing the last cycle take place much 

 nearer the center and at less regular distances from the center. In M. 

 coronula the corallum is higher and the septal denticulations coarser. 



Dimensions (of the type). Diameter 7 mm., height 3 mm. 



Occurrence. MONMOUTH FORMATION (Exogyra costata zone). Bed 

 of small branch seven-eighths of a mile southwest of Brightseat and 

 three-eighths of a mile south of the Sheriff road; about a mile west of 

 Friendly, Prince George's County. 



Collection. Maryland Geological Survey, on deposit in the IT. S. 

 National Museum. 



THALLOPHYTA 



CLASS FUNGI 



order PYRENOMYCETES 



Genus SPHAERITES Unger 



[Gen. et Sp., 1850, p. 37] 



SPHAERITES RARITANENSIS Berry 



Plate LXXXI, Fig. 3 



Sphwrites raritanensis Berry, 1911, Bull. 3, Geol. Survey of New Jersey, 

 p. 62. 



Description. Viewed megascopically these remains appear as oval or 

 circular umbilicate dots from .25 mm. to .5 mm. in diameter, with 

 depressed margin and enlarged central portion, the latter occupying two- 

 thirds of the total diameter. 



