STAUEASI'HIIM. 1 -S^ 



St. pseudooeenatum, Lund. iSt. maamense, Arch.) Pliile 

 XL VIII, figs. 9, 10. 



Cells nearly one-fourth part longer than broad, subov:il 

 ends somewhat truncate, deeply constricted, sinus narjow 

 linear ; semi-cells subsemicircular, base straight, sides sub- 

 crenate, crenae roughly truncate-emarginate; ends obsolete! y 

 erose-dentate, inferior angles subtruncate; in vertical view 

 triangular, sides retuse, angles broadly subtruncate, dentate 

 with three granules. 



Diameter 30-35 yu. ; length 38-42 //. 



Found this species frequent in ponds, Minnesota and Cali- 

 fornia. This form is nearest to St. crenatum, Bailey, (in Eal fs' 

 Br. Des., p. 215,) but differs in liaving a mucli narrower sinus 

 between the semi-cells, and the semi-cells are not cune;\te 

 flabelliform. 



St. eeasum, Breb., var. espinulosa, Lund. Plate XLVIll, 

 figs. 16, 17. 

 Of medium size, as long as broad, coarsely granulate, sinus 

 acute-angled, outwardly ampliated ; semi-cells somewhat 

 elliptic, back nearly straight, angles rounded, more or less 

 dentate, with large granules; in vertical view triangular, 

 angles broadly rounded, sides concave. 

 Diameter 34-38 yu. 



Green's Lake, New Jersey. 



St. lutbolum, Lagh. Plate XLIX, figs. 22, 23. 



Cells rather small, nearly circular, deeply constricted, 

 sinus narrow linear ; base of semi-cell straight, back arched, 

 inferior angles obtusely rounded granulate-crenate. Mem- 

 brane thick, punctate, yellowish. 



Diameter 32 //. ; lengtli 33 yu. ; thickness 32 /<. 

 Tewksbury, Massachusetts. 



St. Cosmarioides, Beinsch. Plate XL VI, figs. 7, 8. 



Cells large, composed in front view of two orbicular semi- 

 cells attached, forming an isthmus of one-third the diameter 

 of the cell ; margins of sides finely dentate ; in vertical view 

 triangular, angles rounded, sides slightly convex. 



Prof. Reinsch deBcribes this form as found in Pennsylvania. 

 To my knowledge it has not occurred since. 



St. polymoephum, Breb. Plate LIII, figs. 9, 10, 24, 25. 



Semi-cells in front view broadly elliptic, with sides taper- 

 ing into short, stout processes, ends tipped with three or 

 four small spines ; membrane rough with minute, sometimes 



