114 THE DIATOM AGILE OF PHILADELPHIA AND VICINITY 



HANTZSCHIA AMPHIOXYS VAR. MAJOR GRTJN. 



Valve as in type, but the keel puncta are 5 in 10 ^ and the striae are 11-12 in 10 p. 

 L. 71 n. 



H. amphioxys var. major Grun. is stated to be 120 M in length. The present form is 

 smaller but corresponds in puncta and striation. Van Heurck remarks that it approaches 

 H. virgata. 



Abundant in sand ripples on the beach at Cape May, N. J. 



PI. 39, Fig. 4. 



Fig. 6, PI. 39, is drawn from an authentic specimen of Wm. Smith's Nitzschia amphi- 

 oxys, from England, and is introduced for comparison. The central nodule is not evident. 



Fig. 3, PI. 39, is from a specimen from an unknown locality. The keel puncta are 6 

 and the striae 16 in 10 p. 



HANTZSCHIA VIRGATA (ROPER) GRUN. 



Valve arcuate on the dorsal side, nearly straight on the ventral side, with rostrate, 

 recurved apices; keel puncta prolonged to one-third the width of the valve, 4 in 10 /u; trans- 

 verse striae, 9-10 in 10 y.. L. 115 n. 



Shark River, N. J. (Kain). 



I have not been able to find this form on our coast. The figure is drawn from a speci- 

 men from another locality. 



PI. 32, Fig. 23. 



HANTZSCHIA MARINA (DONK.) GRUN. 



Valve with dorsal margin slightly arcuate, ventral margin straight; apices rostrate 

 and recurved; keel puncta, 6 in 10 p., prolonged into costae across the entire valve; trans- 

 verse striae, 12 in 10 ju, in double rows of alternating puncta between the costae. L. 106 ju. 



Epithemia marina Donkin. 



Along the coast. 



PI. 32, Fig. 22. 



NITZSCHIA HASSALL (1845), em. GRUN. (isso) 

 (named after Christian L. Nitzsch, of Halle) 



Frustules usually free, sometimes enclosed in tubes or united into a filament. Valves 

 keeled, the keels of the two valves usually diagonally opposite (see Hantzschia) ; keel puncta 

 short or prolonged. 



According to Mereschkowsky, there are at least two endochrome plates placed trans- 

 versely on the zones; sometimes there are from four to six plates, in one species twenty 

 granules and in another no trace of any endochrome whatever. 



The following analysis is that of Grunow as given in Cleve and Grunow's "Arctic 

 Diatoms," and adopted and illustrated by Van Heurck in his "Synopsis." 



GROUPS 



1. Tryblionella. Keel very excentric, valve often folded; keel puncta indistinct, 

 usually the same in number as the striae. 



2. Panduriformes. Valve broad, constricted in the middle, with more or less evident 

 fold; keel very near the edge; keel puncta quite evident or apparently wanting. 



