492 SYSTEMATIC PALEONTOLOGY 



Genus STEPHANOGONIA Ehrenberg. 

 Stephanogonia polygona Ehrenberg. 

 Stephanogonia quadrangula Ehrenberg. 

 Family BIDDULPHI/E. 



Genus BIDDULPHIA Gray. 



Biddulphia ACUTA (Ehrenberg). 



Plate CXXXIV, Fig. 6. 



Triceratium acutum Ehrenberg, 1844, Monatsb. d. k. Akad. d. Wiss., Berlin, p. 272. 

 Triceratium acutum Brightwell, 1853, Quart. Jour. Roy. Mic. Soc, vol. i, p. S.'jl, 



pi. iv, fig. 16. 

 Triceratium acutum Van Heurck, 1881, Syn. Diat. Belg., pi. cviii, fig. 1. 

 Biddulphia acuta Boyer, 1901. Proe. Acad. Nat. Sci. Pbila., vol. lii, p. 706. 



Description. — " Valve triangular, sides slightly convex and processes 

 at the angles somewhat acute. Surface flat, reticulated, cells hexagonal, 

 9. in .01 mm. at the centre, 3 in .01 mm. at the border, not radiate. 

 L. of s. .04 mm. to .123 mm." Boyer, 1901. 



Biddulphia acuta resembles Biddulphia favus (Ehrenberg) which 

 does not occur in the Miocene deposits but is abundant in later deposits 

 and is found living along the coast. The former is, probably, therefore, 

 to be considered as the original or type form. 



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

 Point. Not common. 



Collection. — Maryland Geological Survey. 



Biddulphia Americana (Ealfs). 

 Biddulphia aurita (Lyngbye). 

 Biddulphia condecora (Ehrenberg). 

 Plate CXXXIV, Fig. 7. 



Triceratium condecorum Ehrenberg, 1844, Monatsb. d. k. Akad. d. Wiss., Berlin 



p. 273. 

 Triceratium condecorum Schmidt, 1875, Atlas der Diatomaceen-kunde, pi. Ixxvi, 



fig. 28 (not 27 as given). 

 Biddulphia condecora Boyer, 1901, Proc. Acad. Nat. Sci. Phila., vol. lii, p. 720. 



Description. — Valve triangular with nearly straight sides and obtuse 

 angles. Surface flat or slightly depressed at the center, with rounded 

 puncta arranged in rows which radiate in undulating lines from the 

 center. L. of s. .145 mm. 



