The quadrangular form occurs only southward. Pl. 6, Fig. 6. At "a" a cell showing the lower punctate layer. Pl. 40, Fig. 16, a transverse section of a portion of the valve showing the cellular structure and the punctated lower stratum. {32}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. Pl. 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 µ and sometimes 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. Connective 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 common. Pl. 7, Fig. 6. BIDDULPHIA RHOMBUS (EHR.) WM. SM. Valve rhomboidal, sometimes triangular, with subconical processes. Surface convex with hexagonal reticulations, 7-9 in 10 µ, irregular at the centre and radiating to the circumference. 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. Pl. 7, Fig. 5 (somewhat inclined, as usually seen). BIDDULPHIA SMITHII (RALFS) V. H. Valve orbicular, convex, with reticulations 5 in 10 µ 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 µ in longitudinal 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. Pl. 7, Fig. 7. {33}BIDDULPHIA LÆVIS EHR.