GENUS PAMPHAGUS— PAMPHAGUS IIYALINUS. 195 



broad neck, terminating in a circular mouth. Shell membranous, trans- 

 parent, colorless, structureless, and elastic. Sarcode intimately adherent 

 to the interior of the shell, finely granular, with variable proportions of 

 oil-like molecules, usually more or less accumulated in a median zone, and 

 with more or less vacuoles at the lower part. Nucleus large, and commonly 

 with a large and distinct nucleolus. Pseudopods filamentous, delicate, and 

 furcate. 



Size. — From 0.032 mm. in diameter to 0.048 mm. in length and 0.044 

 mm. in breadth. 



Locality. — In the superficial ooze of ponds, ditches, and lakes. Ob- 

 served in Pennsylvania, New Jersey, and Wyoming Territory. 



In his great work, the 'Infusionsthierchen,' Ehrenberg describes a 

 small rhizopod under the name Arcella hyalina, almost spherical, and with 

 a smooth hyaline membranous shell. It ranges from ~\h. to ith of a line. 

 It exhibited within many vesicles, and possessed many filamentous pseudo- 

 pods. Later what appears to be the same animal was described by 

 Schlumberger with the name of Gromia hyalina, and by Schneider with 

 that of Difflugia hyalina. Recently Hertwig and Lesser have also described 

 the creature, and have referred it to a new genus, with the name of Lecy- 

 thium hyalinnm. In what respect this genus differs from Pamphagus I am 

 unable to see, and therefore have considered it as pertaining to the same. 



Pamphagus hyalinus, as I take it to be, I have occasionally found, 

 though I suspect it is not uncommon, but on account of its inconspicuous 

 character is readily overlooked. It is a minute, spheroidal, translucent, 

 colorless creature, represented in the magnified views of figs. 13-17, pi. 

 XXXIII. The shape is nearly spherical, or it is slightly tapering at the 

 oral pole, or feebly prolonged so as to be sub-pyriform. The mouth is 

 inferior, terminal, comparatively large, circular, and dilatable, and its 

 margin is entire and thin. The shell or membranous investment is struc- 

 tureless and elastic, but not voluntarily extensible or contractile. 



The sarcode is like that of Pamphagus niittabilis, but usually contains a 

 greater proportion of oil molecules collected in the intermediate zone, and 

 a greater number of clear vacuoles in the lower portion. Sometimes the 

 large nucleus is clear and homogeneous, as seen in fig. 14, but in others it 

 has appeared of pale granular constitution, and contained a large distinct 

 nucleolus, as represented in figs. 15-17. 



