246 The Sarcodina 



Fig. 5, 31. Arcellidae: A. Corycia flava (Greef) Penard (80-100/x), elastic 

 membranous test, pseudopodia retracted (after P.). B, C. Hyalosphenia 

 cuneata Stein (60-70^), broad surface of specimen in locomotion, narrow 

 surface of test (after Penard). D, E. Pyxidicula operculata Ehrenberg, view 

 from above, vertical section of test (after Penard). F, G. Pseudochlamys 

 patella Claparede and Lachmann (diameter about -iOfi), specimens seen from 

 above and from side (after Penard). H, I. Cryptodiffliigia compressa Penard 

 (I6-18;tt lo'ig)' broad and narrow surfaces (after P.). J, K. Plagiophrys parvi- 

 punctata Penard (test averages 50yn long), broad and narrow surfaces (after 

 P.). L, M. Cocliliopodium gratiiilatum Penard (test 70-90/i long), lateral and 

 polar views (after P.). N, O. Pamphagus mutabilis Bailey (test usually 70- 

 90^ long), test transparent, elastic, often twisted; in locomotion (N), and view 

 from above (after Penard). 



This system is convenient in that it is based upon fairly obvious char- 

 acteristics, but it ignores such features as structure of the pseudopodia. 

 The family Arcellidae, for instance, includes Arcella and Pseudochlamys 

 with slender lobopodia and also Pamphagus and DifflngieUa with typical 



