504 SYSTEMATIC PALEONTOLOGY 



irregular. Border variable in width, coarsely striate. Diam. av. 

 .108 mm. 



Occurrence. — Calvert Formation. Flag Pond, f mile south of Par- 

 ker Creek, 3 miles north of Parker Creek, Plum Point, ^ mile north of 

 Forest Wharf, Nomini Bay, Chesapeake Beach, God's Grace Point, 

 Fairhaven, 1 mile west of Tracy Landing, 1-| miles southeast of Marriott 

 Hill, 1 mile north of Jewell, 1 mile north of Jones Point, 1 mile south 

 of Chesapeake E. B. Bridge, 1 mile northwest of West River, 1 mile east 

 of Marriott Hill. 



Collection. — Maryland Geological Survey. 



CosciNODiscus asteroides Truan and Witt. 

 Plate CXXXIV, Fig. 14. 



Coscinodiscus asteroides Truan and Witt, 1888, Die Diatomaceen der Polycystin- 



kreide von Jeremie in Hayti, p. 13, pi. iii, fig. 2. 

 Coscinodiscus asteroides Rattray, 1890, Proc. Roy. Soc. Edinburgh, voL xvi, p. 34. 



Description. — Valve circular, flat. Markings hexagonal, arranged in 

 spiral rows, large at the center, suddenly decreasing and then gradually 

 increasing to near the border where they are smaller. 



In specimens from Jeremie, Hayti, " a ring of ten to twelve depres- 

 sions in the middle of the valve " is seen, whence the specific name. In 

 the Maryland forms these star-like depressions are scarcely, if at all, 

 discernible. 



Occurrence. — Calvert Formation, "Cove, Calvert County" (Gre- 

 ville). Plum Point, "Nottingham" (Rattray). 



Collection. — Maryland Geological Survey. 



Coscinodiscus argus Ehrenberg. 



COSCINQDISCUS ASTEROMPHALUS VAR. OMPHALANTHA GrunoW, 



Coscinodiscus bullieus Schmidt. 

 Coscinodiscus biangulatus Schmidt. 

 Coscinodiscus biradiatus Greville. 

 Coscinodiscus borealis Bailey, 

 Coscinodiscus compositus Rattray. 

 Coscinodiscus centralis Ehrenberg. 

 Coscinodiscus concinnus Wm. Smith. 

 Coscinodiscus durnisculus Schmidt. 



