The Diatoms of Nebraska 153 



Perizonium. The thin, unsihcified membrane of a young auxo- 

 spore. 



Phycoxanthin. The brown coloring matter of diatoms. 



Pseudoraphe. A clear longitudinal space in a diatom valve ; same 

 as rachis. 



Pseudostauros. False stauros. The appearance of a stauros in 

 the center of a diatom valve caused by the striations being ab- 

 sent, and hot by the widening of the central nodule. 



Punctate. Consisting of rows of puncta or dots. 



Punctum. PI. puncta. A point or dot. The striations of most 

 diatoms consist of rows of puncta. 



Rachis or rhachis. A longitudinal line on a diatom valve in 

 which there are no striations. 



Raphe. A longitudinal slit in a diatom valve. It is the central 

 line in Navicnla and allied genera. 



Stauroneiform. Having the form of a stauros or cross. 



Stauros. The transversely elongated nodule as in Stauroncis. 



Sulcus. PI. sulci. A groove or depression in a valve. 



Valve. One of the halves of the silicified cell wall of a diatom. 



Ventral. The inner side of a curved diatom, opposed to dorsal. 



INDEX OF GENERA AND SPECIES 



Achnanthes Bory gg 



biasolettiana (Kiitz.) Grun., pi. 13, figs. 490, 491 gg 



hungarica Grun., pi. 13, figs. 483-487 ; pi. 23, fig. 844 98 



lanceolata (Breb.) Grun., pi. 13, figs. 494-499 100 



linearis (W. Sm.) Grun., pi. 13, figs. 4g2, 4g3 loo 



microcephala (Kiitz.) Grun., pi. 13, figs. 488, 489 99 



AclDianfhidium lanccolafiini Breb 100 



lineare W. Sm 100 



microcephahmi Kiitz 99 



Achnanthosigma Reinh 104 



Actiniscus Ehr 42 



Actinoneis CI • 100 



Affines 90 



Amphicampa Rabenh 107 



Amphicampa Ehr 125 



Amphiprora Ehr 107 



alata (Ehr.) Kiitz., pi. 14, figs. 522-525 107 



ornata Bailey, pi. 14, fig. 521 107 



