MEMOIRS. 



Resume of Recent Contrtbutions to our Knowledge 

 of " P'reshwater Rhizopoda." Part IV. Compiled 

 by Wm. Archer, F.R.S. (With Plate VIII.) 



MoNOTHALAMiA {Monostomato) LoBOSA (continued), 



Pseudochlamys patella, Clap, et Lachmann^ = Amphizonella 

 flava, Greeff2 (PI. VIII, figs. 1—3). 



There can be little doubt that the not uncommon rhizopod. 

 identified by Hertwig and Lesser as above is indeed one 

 and the same with Claparede and Lachmann's form, and, 

 with not less doubt, is also identical with that erroneously 

 called Amphizonella flava by GreefF.^ 



The test possesses ordinarily a hollow, dorsally convex 

 discoid figure, somewhat like Arcella vulgaris, but a great 

 deal smaller, its upper or convex side equally and evenly 

 arched. Its colour at the middle is of a brownish yellow 

 (resembling in tint that of the contents of many diatoms) 

 mostly gradually fading off to the margins, which may be 

 quite colourless ; but I have myself frequently seen examples 

 in which the change was abrupt and quite irregular. This 

 colour resides in the test itself. The median portion 

 of the test is thicker, and it gradually thins off to the 

 margin. In many specimens an arcella-like facetting or 

 punctate appearance can be readily made out, gradually 

 disappearing towards the margin ; but in many others this 

 cannot be at all discovered when it has a more or less 

 smooth, but not a glossy, aspect. I believe the appearance 

 of " facetting" or " shagreening" is due to little rounded, 

 closely posed, scattered scrobiculi. 



Ordinarily the test appears of watch-glass shape, that is, 

 deeply concave on one side and correspondingly convex on 

 the other ; the outer or convex side it is which bears the 



' Claparede and Lachmann, 'Etudes sur les Infusoires et les Rhizopodes,' 

 p. 443. 



2 L. c. p. 100, t. iii, f. 1. 



3 Greeff, ' Archiv. f. Mikr. Anat.,' Bd. II, p. 329, t. xviii, f.l9. 



VOL. XVII. NEW SER. ' H 



