506 syste:matic paleontology 



Occurrence. — Calvert Formatiox. Marriott Hill, God's Grace 

 Point, 1 mile north of Jones Point. (i!^ot common). 

 Collection. — Maryland Geological Survey. 



CoscixoDiscus LiXEATUS Elirenberg. 

 Plate CXXXY, Fig. 1. 



Coscinodiscus Uneatus Ehrenberg., 183S, Abhand. d. k. Akad. d. Wiss., Berlin, p. 129. 

 Coscinodisciis Uneaiiix Ehrenberg, lSo6, Mikrogeologie, pL xviii. fig. 'So. 

 Coscinodiscus Uneatus Schmidt, 1S75, Atlas der Diatomaceeu-kuude, pi. lix, tigs. 



29, 30; pL cxiv, tig. 13. 

 Coscinodiscus Uneatus Rattray, 1S90, Proc. Roy. Soc. Ediubuigh, voL xvi, p. 24. 



Descriptian. — Yalve circular with a narrow border of minute granules 

 7 in .01 mm. Surface nearly flat, with hexagonal markings, 3 in .01 

 mm., arranged in almost straight parallel rows. Diam. .105 mm. 



Occurrence. — Calvert Formatiox. -J mile north of Forest Wharf, 

 Lyons Creek, God's Grace Point, 1 mile north of Jones Point, 1 mile 

 west of Tracy Landing. 



Collection. — Maryland Geological Survey. 



CoscixoDiscus MARGIXATUS Ehrenberg. 

 CoscixoDiscus xoTTiXGHAMEXSis Grunow. 

 CoscixoDiscus ocuLus-iRiDES Ehrenberg. 

 COSCIXODISCUS RADiATUS Ehrenberg. 

 Coscinodiscus symbolophorus Grunow. 

 COSCIXODISCUS SECERXEXDUS Sclimidt. 

 COSCIXODISCUS suBTiLis Ehrenberg. 



COSCIXODISCUS PERFORATUS Ehrenberg. 



Plate CXXXV, Fig. 2. 



Coscinodiscus perforatus Ehrenberg, 1844, Monatsb. d. k. Akad. d. Wiss., Berlin, 



p. 78. 

 Coscinodiscus perforatus Ehrenberg, 1856, Mikrogeologie, pi. xviii, fig. 46. 

 Coscinodiscus pei-forat us Schmidt, 1875, Atlas der Diatomaceen-kunde, pi. Ixiv, figs. 



12-14. 

 Coscinodiscus perforatus Rattray, 1890, Proc. Roy. Soc. Edinburgh, vol. xvi, p. 123. 



Description. — ^Yalve circular. Surface flat; markings angular, some- 

 times granular toward the border, larger at the semi-radius, with distinct 

 central dots. Border narrow, striated. Central space large, irregular. 

 Diam. av. .105 mm. 



