66 THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 



AMPHORA AREOLATA GRUN. 



Valve with straight ventral margin; median line straight, approximate to the ventral 

 margin; axial area indistinct; several longitudinal lines crossed by apparent costae which 

 alternate with rows of fine puncta. 



Blue clay. Rare. 



PI. 15, Fig. 11. 



HALAMPHORA 



AMPHORA COFF^EIFORMIS (AG.) KUETZ. 



Frustule lanceolate, truncate; zone with numerous divisions. Valve arcuate on the 

 dorsal and nearly straight on the ventral side; ends protracted or slightly capitate. 

 A. aponina Kuetz. 

 A. salina Wm. Sm. 

 Along the coast. 

 PI. 15, Figs. 8 and 18. 



OXYAMPHORA 

 AMPHORA LINEOLATA EHR. 



Frustule membranaceous, elliptical, truncate, with broad ends. Zone with numerous 

 divisions. Dorsal part striated transversely; ventral side with longitudinal lines. 

 A. plicata Greg. 



A. hyalina H. L. Smith, Type No. 64. 

 Along the coast. 

 PL 15, Figs. 9 and 10. 



AMPHORA OSTREARIA BREB. 



Frustule oblong, with rounded angles. Zone with five or more divisions transversely 

 striated. Central area narrow, biarcuate; central nodule dilated to a stauros. Valve nar- 

 row, with arcuate dorsal and straight ventral margin, acute at the ends. Striae transverse, 

 finely punctate. 



A. vitrcea CL; A. porcellus Kitton; A. quadrata Breb.; A. elegans Greg. Appearance 

 varies according to the position of the valve. 



Along the coast. 



PL 15, Figs. 12 and 21. 



AMPHORA I^EVIS GREG. 



Frustule oblong, hyaline and membranaceous. Valve linear or slightly arcuate, with 

 ventral margin tumid in the middle; ends obtuse; central nodule dilated to a stauros; 

 median line very narrow, biarcuate, coinciding with the dorsal margin at the ends; striae 

 transverse, punctate. 



Blue clay. 



PL 15, Fig. 13. 



AMPHORA ACUTA GREG. 



Valve lunate, with acute ends; ventral margin straight; ventral side very narrow. 

 Central nodule dilated to a stauros; striee transverse, punctate. 

 Along the coast. 

 PL 15, Fig. 20. 



