STAURASTRTTM. 123 



triangular; from tli< * vertex, triangular, with the angles some- 

 what tumid and rounded; angles furnished with a very large, 

 acute, robust spine. 



Diameter with the spines, 62 ft. 



This species was first found by Lewis, in Saeo Lake, N. H., 

 and since only in one locality, the past Summer, L883, by 

 Miss Eloise Butler of Minneapolis, Minn. 



St. cuspidatum, Breb. Plate XL, tigs. 23-25. 



Sendee]].-, smooth, fusiform, connected l>v a long narrow 

 band; aculei parallel or converging; end view triangular, or 

 rarely quadrangular, with inflated aculeated lobes. 

 Diameter 25 ><; length 30 u. 



Quiet water-, Pennsylvania and New Jersey, hut not frequent. 



St. trihedrale, Welle. Plat.' XL, figs. 12, 13. 



Small punctate-granulate ; semicells, in front view ami in 

 end view triangular, angles rounded, sides concave, sinus 

 narrow linear. 

 Diameter 30 u. 



* 



Pond, Mount Everett, Ma. 



This species in front view, has the appearance of a ('<>smn- 

 fiiini near retusum, Perty, and angustatum, Nord., but the side 



and end views are distinct. The semicells are three sided, 

 pyramidal forms unlike those of a Cosmarium. 



St. tripidum, Nord. Plate XL. figs. 28, -"'. 



Cells about as broad as long, deeply constricted ; semicells 

 short cuneate, with end- dilated, and lightly refuse; superior 

 angles obtuse trisected ; viewed from vertex triangular, angles 

 truncate, trifid; sides somewhat concave; membrane finelv 

 punctate. 



Diameter 30-50 /'. Variable in size. 



Not frequent, but met with in localities widely separated, 

 Pennsylvania, New Jersey, and other States. 



St. Avicula, Breb. Plate XL, figs. 30, 31, 32. 



Semicells twice a- broad a- long with a forked spine on 

 each side ; each angle in end view, terminated by a simple or 

 forked spine ; eytioderm smooth. 



Diameter 25-30 ". without the spine-. 



Rather common species : appears to be found frequently in 

 every Stale in which explorations are made. 



