Valve elliptical; areas semilanceolate; striæ about 11 in 10 µ, sometimes longer and shorter on the margin; short rows of transverse striæ along the axial area. Blue clay. Pl. 25, Fig. 12. _Var. circumsecta Grun._--As in the type but with the lateral areas faintly striate or punctate. _Var. manca A. S._--Valve lanceolate-elliptical, the lateral areas narrow and convergent toward the ends; short rows of transverse striæ along the axial area; striæ, 9 in 10 µ; central pores incrassate. Blue clay. Pl. 25, Fig. 11. NAVICULA LYRA EHR. Valve elliptical, with rounded, sub-rostrate or sub-cuneate ends; lateral areas narrow; striæ, 6 to 14 in 10 µ (Cl.), punctate. L. 50-180 µ. _Var. ehrenbergii Cl._--Lateral areas constricted in the middle, divergent at the ends. Cleve refers to Schmidt, Atlas, Pl. 2, Fig. 25, which is not divergent at the ends. Along the coast. Pl. 25, Fig. 10. A narrower form occurs which has the areas divergent. _Var. ?_--Valve elliptical, lateral areas narrow, convergent at the ends with short rows of punctate striæ; marginal striæ, 10 in 10 µ, punctate. L. 60 µ. Squan River, N. J. Pl. 20, Fig. 5. _Var. dilatata A. S._--Valve elliptical, rostrate; lateral areas convergent in the middle and nearly parallel or convergent at the ends. Blue clay. Pl. 25, Fig. 13. N. lyra is exceedingly variable in outline, fineness of striation and in the lateral areas. Intermediate forms occur approaching N. hennedyi and N. spectabilis. In N. hennedyi the lateral areas are broad, semilanceolate, not narrowed in the middle. In N. spectabilis the lateral areas are broad and narrowed in the middle. In N. lyra the lateral areas are narrow and either constricted or not in the middle. In many forms in {94}these three species the lateral areas are more or less striated or punctate. Cleve does not consider this a distinction of any importance, although certain varieties are founded upon it. All three species are very common in the blue clay and along the coast, but their varieties are too numerous to describe or figure. NAVICULA SPECTABILIS VAR. EMARGINATA CL. Valve elliptical; lateral areas broad, narrowed in the middle, delicately striated; marginal striæ, 10 in 10 µ. L. 70 µ. Blue clay. Pl. 25, Fig. 7. NAVICULA PYGMÆA KUETZ. Valve elliptical, appearing hyaline; axial and central areas faint; lateral areas convergent in the middle; striæ indistinct, about 25 in 10 µ. L. 23 µ. Brandywine Creek (Palmer). Pl. 27, Fig. 23. DECUSSATÆ CL. Valve elliptical or lanceolate; axial area narrow; central area small; striæ punctate, in transverse and oblique, curved rows. NAVICULA PLACENTA EHR. Valve elliptical, with short, rostrate-capitate ends; axial area narrow; central area elliptical; striæ in two directions, the transverse about 22 (to 27, Cl.) in 10 µ, the oblique striæ crossing in both directions in curved lines appearing "coarser than the transverse" (Lewis).