Sketch of the Infusoria of the family Bacillaria. 295 



4. Euastrum . (Fig. 25, PL 1.) This very elegant form is 



somewhat rare. It occurs at West Point with the preceding. 



5. Euastrum . (Fig. 26 and fig. 27, a, Z», c, and cZ, PI. 1.) I 



suspect that the species represented in figs. 26 and 27, is the same as 

 the Echinella oblonga of Greville, which he describes as being " com- 

 pressed, oblong crenato-pinnatifid, and lobed, divided transversely al- 

 most to the centre." (Brit. Flora, Vol. V, p. 398.) 



Fig. 27, a and 6, show two positions of the same individual ; 

 c and d show small individuals, which are probably the young of 

 this species. Fig. 26, although much more deeply lobed than 

 fig. 27, is probably only an older state of the same. They occur 

 at West Point, also near Detroit, Michigan, and in Ouisconsin. 



6. Euastrum . (Fig. 28, «, i.) This species is neither lobed 



nor undulate ; but while the general outline is convex, a minutely ser- 

 rated edge may be seen. When thrown on its side, (fig. 27, 5,) it pre- 

 sents an unusual thickness. 



If this species is compared with fig. 38, PI. 1, the close rela- 

 tion existing between the genera Closterium and Euastrum will 

 be manifest. 



7. Euastrum . (Fig. 29, PL 1.) I suspect that the bodies 



represented in fig. 29, belong to this genus. They consist usually of 

 four somewhat elliptical green bodies placed parallel to each other, and 

 united laterally, as seen in the figure. Each elliptical portion is biden- 

 tate at the ends. I have met with specimens in which eight such cor- 

 puscles were united, producing such an appearance as would be given 

 if a figure like that shown in fig. 29, had a similar one added immedi- 

 ately below it. 



If this is a species of Euastrum, perhaps it may be thus char- 

 acterized ; Euastrum . Fig. 29. Binary (or sometimes 



quaternary,) each corpuscle divided by deep lateral sinuses into 

 two transverse somewhat elliptical bidentate portions, the middle 

 portions longest. Occurs in ponds near West Point. 



8. Euasirum margaritiferum, Ehr. (Fig. 8, a, b, PL 1.) Body bi- 

 nary, elliptical, each part semi-orbicular with the margin entire, y^^r to 

 gJf line. Hctcrocarpella tetropthalma, Ktz. Linn. 1833, PL 19, fig. 87. 



Our species (fig. 8) agrees pretty well with the above descrip- 

 tion and with Kutzing's figure. A figure given by Meyen in his 

 PHanzen Physiologic, Vol. Ill, PI. 10, fig. 31, apparently belongs 

 to this species also. 



Tlie surface has a great number of minute hemispherical pro- 

 jections, disposed in a quincuncial order. It is possible that the 



