96 FRESH-WATER RHIZOPODS OF NORTH AMERICA. 



longation to the margin of the mouth. Nucleus single, situated near tne 

 fundus of the endosarc. Contractile vesicles several, situated at the 

 periphery of the latter, contiguous to the nucleus. Pseudopods usually up 

 to half a dozen or more, cylindrical, simple or branching, commonly 

 rounded at the ends, sometimes spreading and pointed. 



DIFFLUGIA GLOBULOSA. 



Plates XV, figs. 25-31 ; XVI, figs. 1-24. 



Difflugia globulosa. Dujardin : An. Se. Nat. 1837, viii, 311, pi. ix, figs, la, b; Hist. Nat. Iufusoires, 1841, 

 248, pi. ii, fig. 6. Pritchard : Hist. Infusoria, 1861, 554, pi. xxi, fig. 10. 



Difflugia proteiformis. Ehrenberg: Infusionsthierchen, 1838, 131, Tat', ix, Fig. i; Mi orographic Diet. 1860, 

 232, pi. 23, fig. 39.— Pritchard : Infusoria, 1861, 553.— Leidy: Proc. Ac. Nat. Sc. 1877,307. 



Difflugia globular!*. Wallich: An. Mag. Nat. Hist, xiii, 1864, 241, pi. xvi, figs. 1, 2, 17, 27.— Leidy: Proc. 

 Ac. Nat. Sc. 1877, 307, 321. 



Difflugia proteiformis, subspecies D. globularis. Wallich: Ibidem. 



Difflugia acrojiodia. Hertwig and Lesser: Arch. mik. Anat. 1874, x, Supl. 107, Taf. ii, Fig. 6. 



Shell spheroidal or oval, with the oral pole more or less truncated. 

 Mouth inferior, terminal, circular, usually truncating the shell; sometimes 

 more or less protruding or bordered by a short neck, rarely more or less 

 inverted. Shell commonly composed of quartz-sand, sometimes of diatoms, 

 and sometimes of chitinoid membrane usually incorporated with more or 

 less sand and diatoms. Sarcode, independent of the food, colorless. 



Size. — Smallest specimen, with shell of sand, 0.036 mm. long by 0.03 

 mm. broad ; with the mouth 015 mm. wide. Chitinoid specimens, with 

 diatoms and sand, from 0.024 mm. long by 0.032 mm. broad; with the 

 mouth 0.016 mm. wide, to 0.108 mm. long, 0.12 mm. broad; with the mouth 

 0.06 mm. wide. Largest specimens, of sand grains, 0.26 mm. long, 0.184 

 mm. broad, with the mouth 0.08 mm. wide. 



Localities. — In the ooze of ditches and ponds frequent, in the vicinity 

 of Philadelphia, Pennsylvania, New Jersey, Maine, Rhode Island, Connec- 

 ticut, Florida, Alabama, Nova Scotia, Utah, and near Fort Bridger and 

 in the Uinta Mountains, Wyoming Territory. Small forms are not unfre- 

 quent on moist earth in bogs, meadows, and even, with alga? and mosses, in 

 the crevices of the brick pavements of the city of Philadelphia. 



Dujardin, in 1837, described a species with the name of Difflugia 

 globulosa, in which he says the shell is corneous, globular, and 0.1 mm. 

 long. Of the accompanying figures, one is ovoid, with the mouth at the 

 narrower end ; the other is represented as an upper view, and is oval, so 



