Valve narrow, linear; axial area broad, widened into a transverse fascia; striæ, 8 in 10 µ. L. 32 µ. Fresh water. Pl. 30, Fig. 24. TABELLARIÆ PINNULARIA STOMATOPHORA (GRUN.) CL. Valve linear, with rounded ends; axial area less than one-third the width of the valve, gradually widened in the middle to a transverse fascia; on each side of the central nodule is a lunate space; striæ divergent in the middle, convergent at the ends, 13 in 10 µ; terminal fissures very long, bayonet shaped. L. 75 µ. Cleve describes a variety continua as not interrupted. In some forms the fascia is marked by very faint, short striæ on the margin. Fresh water. Newtown Square. Pl. 30, Fig. 12. PINNULARIA GIBBA (KUETZ.) V. H. Valve linear, tapering to the subcapitate ends; axial area dilated in the middle; striæ, 10-11 µ, divergent in the middle, convergent at the ends. L. 80 µ. Fresh water. Pl. 30, Fig. 5. PINNULARIA MESOGONGYLA (EHR.) CL. Valve linear, gibbous in the middle, ends subcapitate; axial area narrow, widened in the middle to a large orbicular space; striæ strongly divergent in the middle, convergent at the ends, 11 in 10 µ. L. 60 µ. Fresh water. Common. Pl. 30, Fig. 6. {110}PINNULARIA STAUROPTERA (GRUN.) CL. Valve linear, with slightly triundulate margins tapering to the subcapitate ends; axial area more than one-third the width of the valve, slightly widened in the middle; median line with approximate central pores and semicircular terminal fissures; striæ divergent in the middle, convergent at the ends, 11 in 10 µ. L. 82 µ. May's Landing, N. J. Pl. 30, Fig. 13. Some of the forms are more triundulate than the specimen figured. PINNULARIA STAUROPTERA VAR. INTERRUPTA CL. Valve linear, tapering to the subcapitate ends; axial area broad, widened in the middle to a transverse fascia; striæ divergent in the middle, convergent at the ends, 10 in 10 µ; median pores approximate. L. 118 µ. Schuylkill River. Pl. 30, Fig. 11. PINNULARIA TABELLARIA (EHR.) CL. Valve linear, gibbous in the middle and tapering to the subcapitate ends; axial area about one-third the width of the valve, widened in the middle; median line with approximate central pores and bayonet-shaped terminal fissures; striæ sometimes unilaterally interrupted, divergent in the middle, strongly convergent at the ends, 9 in 10 µ. L. 138 µ. Blue clay. Rare. Pl. 30, Fig. 9. The form here figured has coarser striæ than in the type which is also usually more capitate.