72 THE DIATOMACE/E OF PHILADELPHIA AND VICINITY 



GOMPHONEMA CONSTRICTUM EHR. 



Valve clavate, constricted beneath the abruptly rounded apex, gibbous in the middle, 

 strise alternately longer and shorter; axial area narrow, central area unilateral, with one 

 stigma. 



Common in fresh water. 



PL 19, Fig. 8. 



GOMPHONEMA SPH^EROPHORUM EHR. 



Valve clavate, with capitate or rostrate-capitate apex and narrow basis; axial area 

 very narrow; central area small, unilateral, with one stigma. 



Common in fresh water. 



PI. 19, Figs. 9 and 10. Fig. 10 appears to be a transitional form having a more distinct 

 axial area and rostrate apex. 



GOMPHONEMA AUGUR EHR. 



Valve broadly clavate, truncate and apiculate at the apex; basis sub-acute; axial area 

 distinct; central area small, unilateral with one stigma; stria? with distant puncta. 

 Blue clay. Willistown, Pa. 

 PL 19, Fig. 21. 



GOMPHONEMA INTRICATUM KUETZ. 



Valve narrow, lanceolate, slightly gibbous in the middle; axial area distinct; central 

 area transverse with one stigma; strise parallel. Quite variable. 

 Common in fresh water. 

 PL 19, Fig. 14. 



GOMPHONEMA ANGUSTATUM KUETZ. 



Valve lanceolate, with sub-rostrate apex and basis; axial area indistinct; central area 

 unilateral, with one small stigma; strise slightly radiate, indistinctly punctate. 

 Very common in fresh water. 

 PL 19, Figs. 18 and 19. 

 Fig. 19, as stated above, represents the formation of an auxospore. 



GOMPHONEMA ^QUALE GREG. 



Valve linear-lanceolate, nearly symmetrical, with capitate apex and basis; axial area 

 narrow; central area unilateral, with one stigma; strife radiate in the middle, slightly con- 

 vergent at the ends. 



Gomphonema intricalum var. cequale (Greg.) Cl. 



Blue clay. Not common. 



PL 19, Fig. 15. 



GOMPHONEMA SARCOPHAGUS GREG. 



Valve linear, irregular in outline, with rounded apex and basis; axial area distinct; 

 central area small, unilateral, with one stigma; stria? irregular with coarse, distinct puncta. 

 Occasional in fresh water. 

 PL 19, Fig. 16. 



GOMPHONEMA CAPITATUM EHR. 



Valve clavate, broad at the sub-truncate apex and slightly constricted, or with paral- 

 lel margins; axial area linear, central area stellate, with one stigma; strise in the middle 

 alternately longer and shorter. 



Blue clay. 



PL 19, F~ig. 22. 



