138 DESMIDS OF THE UNITED STATES. 



St. nantm, Wolle. Plate XLIY, figs. 8, 9, 10. 



Very small, smooth, or granulate-punctate; semicells sub- 

 cuneate, sides some what rounded, ends broadly convex ; superior 

 angles produced Laterally into straight, slightly diverging arms, 

 nearly as long as the diameter of the cell, ends forked ; viewed 

 from the end tri-radiate, sometimes twisted so that the arms of 

 the lower half cell alternate with those of the upper half. 



Diameter 20-25 ,". 



Frequent in ponds, Mi. Everett, Mass. 



This minute species is nearest St. graeile, Halts, but diners 



in its smaller size, more forked apices, and smoother mem- 

 brane. 



St. vkstitim, Ralfs. Plate XLY. figs. 28, 29, 30. 



Cells rough with minute granules; with this investment 

 there are also minute emarginate spines ; semicells fusiform in 

 front view ; seen from the vertex, triradiate, each side having 

 two slender, forked spines in the middle, and often accompanied 

 by other -mailer ones. 



Diameter 62 90 u. 



Has a home in many parts of the civilized world, so here 

 also it is found widely scattered. 



Sr.SEBALDi,(>&incfo*>8fe6aWi),Reinsch. Plate XL VI, figs 1 6; L0. 

 ( me-fourth to one-half wider than lone, coarsely granulate ; 

 margins in part gran ulate-crenate, and in part spinous. Semi- 

 cells- broad cuenate, base truncate, top convex, with sides more 

 or less conically produced ; apices bifid or trifid ; near the top 

 margin, a series of emarginate <r tricuspidate -pine-, which 

 come t> view at one or the other end of the cell as it i- more 

 or Less inclined from a horizontal position. End view trian- 

 gular, angles slightly produced, apices tridentate; sides aearrj 

 straight, or slightly convex. 



Diameter 7695 ,". 



A conspicuous specie-, large, stout and spinous; variable 

 in the length of the lateral arms ; in some cases short stumpy, 

 in others more elongated; the -pine- are also variously prom- 

 inent; in exact horizontal position they are often not notice- 

 able; when somewhal turned they become prominent on one 



