THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 59 



along the connective zone. It is necessary, therefore, to distinguish between A. longipes 

 and the following group, but, because of the long continued union of all of the stipitate 

 forms having the general appearance of a true Achnanthes, I shall continue to describe the 

 local species under the generally accepted name. 



ACHNANTHES BREVIPES AG. 



Valves without costae; striae moniliform; upper valve with excentric pseudoraphe or 

 median line; otherwise as in A. longipes. 

 Along the coast, in estuaries. 

 PL 16, Fig. 3. 



ACHNANTHES SUBSESSILIS KTJETZ. 



Valves linear-elliptical, rounded at the ends; upper valve with excentric pseudoraphe; 

 striae moniliform, puncta smaller than in A. brevipes. 



Along the coast, in estuaries. 



PL 16, Figs. 4, 5, 6. 



The three species described above are named from the length of the stipe, but this 

 varies considerably and is not of special significance. 



ACHNANTHES INFLATA (KXJETZ.) GRUN. 



Valves more or less inflated in the middle, usually with the stauros of the lower valve 

 asymmetrical and wider than in A. subsessilis, with which it agrees in size and markings. 

 Gloucester, N. J. (artesian well). 

 PL 16, Figs. 7 and 8. 



ACHNANTHES COARCTATA (BREB.) GRUN. 



Valves lanceolate, oblong, broad at the ends and constricted in the middle. Stauros 

 wide; pseudoraphe of the upper valve excentric; striae slightly radiate on the lower valve; 

 puncta small. 



Blue clay. 



PL 16, Fig. 9. 



ACHNANTHES LANCEOLATA (BREB.) GRUN. 



Valves more or less elliptical; strise radiating, 12 in 10 n, punctate; on the lower valve a 

 horse-shoe shaped hyaline space on one side of the centre; on the upper valve an irregular 

 stauros, not reaching the margin. L. 8-20 p. 



In springs. Abundant at Newtown Square. 



PL 16, Figs. 10, 11, 12. 



ACHNANTHES EXIGUA GRUN. 



Valves oblong-lanceolate, with rostrate ends, sometimes slightly constricted in the 

 middle. Stauros rather wide; striae punctate, radiating, 22 in 10/*. L. 10-12 ju. 

 Stauroneis exilis Kuetz. (not Achnanthes exilis Kuetz). 



Frequently found in aquaria where I have kept it growing continuously for years. 

 PL 16, Figs. 14 and 15. 



ACHNANTHES LINEARIS FORMA CURTA H. L. SMITH 



Frustules solitary or geminate. Valves linear-elliptical, or elliptical-lanceolate. Lower 

 valve without distinct axial area; upper valve with axial area widened in the middle; striae 

 slightly radiate (?). L. 7 ju. One of the smallest of diatoms. 



