The Diatoms of Nebraska 107 



27. Amphiprora 



Amphiprora Ehr. Amer., p. 11^. 184^; Amphicampa Rabenh. ; 

 Amphitropis Pfitz. ; Entomoncis Ehr. 



Etym., from Gr. d^^i, both, and -n-poipa, the prow of a boat, so 

 called on account of the two-winged margin of the cells. 



Cells single, free; twisted, lanceolate in valve view, hour-glass 

 shape in girdle view with a sigmoid girdle ; interzones present ; 

 valves convex with a raphe concealed in a sigmoid, emarginate 

 keel ; central and terminal nodules present ; valves transversely 

 striate, rarely scattered-punctate. Chromatophore a single large 

 plate lying next to the girdle. 



A. Keel undulate. i. A. ornahi. 



AA. Keel not undulate. 2. A. data. 



1. Amphiprora ornata Bailey. Micro. Ohs. in S. C, p. 38, pi. 2, 



figs. 15, 23. 1850. 



PI. 14, fig. 521. 



Valves membranous, thin, deeply constricted in the middle in 

 girdle viev/, twisted around the longitudinal axis, 45-80 ju, long, 

 34-50 /A wide; keel undulate; striations radiate, finely granular, 

 20-22 in 10 /a; connecting zone with 8-10 well-marked plaits. 



In Schimmer's Lake, Grand Island. 

 Stockton, Cal. 



2. Amphiprora alata (Ehr.) Kiitz. BacilL, p. lo/, pi. 3, fig. 63. 



18^4. 



Navicula alata Ehr. Bcr., p. 18. 1840. 



PI. 14, figs. 522-525. 



Linear-elliptic with apiculate apices. 50-130 /x long, 20-47 /x, 

 wide; keel sigmoid, not undulate, furnished with elongated dots, 

 about 4 in 10 /a; striations fine, granular, 11-16 in io/a; cells usu- 

 ally twisted around the longitudinal axis, hour-glass shape in girdle 

 view. Fig. 524 shows process of dividing. 



In Salt Creek, Lincoln ; Little Salt at Arbor ; with Oscillatoria at Omaha ; 

 and at Ashland and Fairbury. 



28. Gomphonema. 



Goiuphoncuia Ag. Syst. Alg., p. 75. 1824. Crystallia Som- 

 merfels ; Dcndrclla Bory ; Diomphala Ehr. ; Gomphoncis 



