114 Clarence J. Elmore 



Corn Creek, S. Dak. ; fresh water near Devils Lake, N. Dak. ; New- 

 Concord, Ohio ; Emporia, Kansas. 



14. Gomphonema exiguum Kiitz. Bacill., p. 84, pi. jo, fig. 58. 

 1844. 



PI. 15, figs. 575-576. 



Clavate or cuneate, 10-25 /^ long, 2-3^11 wide, apex rounded, 

 obtusely angular, or slightly rostrate, base more acute; striations 

 nearly transverse, 15-18 in 10 /x, extending nearly to the raphe and 

 leaving a very narrow hyaline space which is slightly wider oppo- 

 site the central nodule. 



This is a marine species, but Schonfeldt, Bacill., p. 12 j, reports 

 it in fresh water. 



In shell marl, Loup City. 



29. Rhoicosphenia 



Rhoicosplicnia Grun. in Wien. Verh., X, p. ^11. i860. 



Etym., from Gr. poiK6<i, curved, and acjiyv, wedge, an appropriate 

 name, the cells being wedge-shape like Gouiphoncnia, but curved. 



Cells mostly stalked, cuneate in both girdle and valve view, 

 curved in girdle view ; interzones present, valves straight, bilater- 

 ally symmetrical, transversely striate, unlike, the concave valve 

 with raphe and central and terminal nodules, the convex valve 

 without nodules and with a pseudoraphe. Chromatophores and 

 auxospores as in Gomphonema. 



Rhoicosphenia curvata (Kiitz.) Grun. Alg. Nov., p. 8. i86y. 



Gomphoncina curvatiim Kiitz. Linnaca, X, p. 5(5/, pi. 16, fig. 

 57. 1833. Syn., p. 3Q, fig. 5/. 1834. 



PI. 15, figs. 577-581- 



Cuneate or spatulate, 15-27 /* long, 3-8 /a wide, upper end 

 rounded or slightly capitate, lower end more acute, but often 

 capitate ; upper valve with nearly parallel but slightl}^ radiate stri- 

 ations, 9—10 in 10 ju., reaching to the pseudoraphe, no raphe or 

 nodules; lower valve with striations slightly radiate. 10-14 iii lO/*) 

 extending nearly to the raphe, but slightly shortened opposite the 

 central nodule. 



In springs, creeks, rivers, etc., with Ulothriv, Cladophora, or other 



