32 THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 



BIDDULPHIA ANTEDILUVIANA (EHR.) V. H. 



Frustules quadrangular, sometimes united in zig-zag chains. Valve quadrangular 

 with more or less concave sides, sometimes cruciform. Surface with angular cells arranged 

 in concentric and radiating lines increasing toward the circumference. At each angle is a 

 large, rounded process, which, as well as the secondary layer, scarcely visible, is finely 

 punctate. 



Amphitetras antediluviana Ehr. 



Amphitetras tessellata Shad. 



Blue clay. Rare. 



PI. 6, Fig. 3. 



A cruciform variety occurs at Pensauken, N. J., artesian well (Coll. F. J. Keeley). 



BIDDULPHIA GRANULATA ROPER 



Valve elliptical-lanceolate, convex, with diagonal rows of puncta 12 in 10 n and some- 

 times with small scattered spurs. Processes inflated at the base, obtuse at the ends, which 

 are curved outward toward alternate sides. Near each process and on opposite sides of the 

 longitudinal axis is placed a stout spine bent or curved inward near the middle. Connec- 

 tive zone with diagonal rows of puncta smaller than those on the valve. 



Pavonia, N. J., artesian well. Fossil in the Pleistocene. Along the coast. Not com- 

 mon. 



PI. 7, Fig. 6. 



BIDDULPHIA RHOMBUS (EHR.) WM. SM. 



Valve rhomboidal, sometimes triangular, with subconical processes. Surface convex 

 with hexagonal reticulations, 7-9 in 10 M, irregular at the centre and radiating to the circum- 

 ference. Minute spurs are scattered over the surface, and on each side are usually two or 

 three short spines. 



Common along the coast and fossil in the Miocene and later deposits. 



PI. 7, Fig. 5 (somewhat inclined, as usually seen). 



BIDDULPHIA SMITHII (RALFS) V. H. 



Valve orbicular, convex, with reticulations 5 in 10 p. radiating from the centre and 

 decreasing toward the margin and processes which are truncate. A short spine is found on 

 each side half way between the processes. Zone narrow with fine puncta 12 in 10 M in lon- 

 gitudinal rows. 



Cerataulus smithii Ralfs. 



Eupodiscus radiatus Wm. Sm. 



Blue clay. Along the coast southward. 



PL 7, Fig. 8. 



BIDDULPHIA TURGIDA (EHR.) WM. SM. 



Valve elliptical or orbicular, surface convex. Processes very large, cylindrical, placed 

 obliquely and inclined by the torsion of the frustule. Between the processes are two stout 

 spines, one on each side, frequently forked at the ends. Puncta fine, irregular at the centre 

 and radiating toward the circumference. 



Cerataulus turgidus Ehr. 



Blue clay. Along the coast. Quite variable in size. 



PI. 7, Fig. 7. 



