124 FRESH-WATEE EHIZOPODS OF NORTH AMERICA. 



I have not been able to ascertain whether these actually merge into 

 each other. 



The range in size of Difflugia constricta is considerable. The smallest 

 measured was ith of an inch long from the anterior lip to the fundus, the 

 breadth was slightly less than the length, and the thickness or fore. and aft 

 diameter of the fundus ^th of an inch, and the mouth was ^th of an inch 

 wide. The largest was ^th of an inch long from anterior lip to fundus, 

 ith of an inch broad, ith of an inch thick, and the mouth 2 ^ th of an inch 

 wide. The spines of the fundus reach a length of ~\h of an inch. 



DIFFLUGIA SPIRALIS. 



Plate XIX, figs. 1-23. 



Difflugia. Leclerc: Mem. Mus. Hist. Nat. 1815, ii, 474, pi. 17, figs. 1 and 4. 



Difflugia spiralis. Ekrenberg: Monatsb. d. Berlin. Akad. d. Wissens. 1840, 199; Abhand. Akad. Wissens. 

 Berlin, 1871, 274, Taf. iii, Fig. 25-27.— Bailey : Micros. Obs., in Smithson. Contrib. 1850, 41.— 

 Fresenius : Abhand. Senckenb. Natorf. Gesells. ii, 1856-8, 224, Taf. xii, Fig. 37-42.— Pritekard : 

 History of Infusoria, 1861, 553.— Carter: An. Mag. Nat. Hist, xiii, 1864, 18, pi. i, fig. 9.— 

 Wallich: An. Mag. Nat. Hist, xiii, 1864, 215— Leidy: Pr. Ac. Nat. So. 1874,79; 1877,307. 



Lcequereusia jurassiea. Schluinberger: An. Sc. Nat. 1845, 255. 



Difflugia proteiformis, monstrosa. Perty : Kenntniss kleinster Lebensformen, 1852, 187, 214, Taf. viii, Fig. 22. 



Difflugia Helix. Cobn : Zeitsck. f. wissens. Zoologie, 1853, 261. 



Difflugia proiciformis, var. scptifera. Wallich: An. Mag. Nat. Hist. 1853, xi, 1853, 453, pi. x, fig. 12. 



Difflugia proteiformis. Wallick : An. Mag. Nat. Hist. 1863, xii, 456. 



Difflugia proteiformis, subspecies!), mitriformis, var. 0. D. spiralis. Wallick: An. Mag. Nat. Hist. 1864, 

 xiii, 1884, 240, pi. xvi, figs. 24, 25. 



D. Corlicella spiralis. Ekrenberg: Abk. Ak. Wis. Berlin, 1871, 247. 



Shell retort-shaped, usually with a laterally compressed spheroidal 

 body, and a short, wide, cylindroid neck, obtuse fundus, and terminal circu- 

 lar or slightly oval mouth. A partition occupying the interior of the shell, 

 defining the neck from the body, and giving to the shell by transmitted 

 light the appearance of a single turn of a spiral. Structure of the shell 

 variable; frequently of quartz-sand, often of peculiar elements, or of chit- 

 inoid membrane incorporated with various extraneous particles. Sarcode 

 colorless; pseudopods as usual in the genus. 



Size. — Length 0.096 mm. to 0.188 mm.; breadth of body 0.068 mm. 

 to 0.164 mm.; thickness 0.068 mm. to 0.136 mm. 



Locality. — Lakes, ponds, and ditches. Pennsylvania, New Jersey, 

 Rhode Island, South Carolina, Georgia, Florida, Alabama, and the Uinta 

 Mountains of Wyoming Territory. 



Difflugia spiralis, a common and pretty species (figs. 1-23, pi. XIX), 

 is one of the most remarkable forms of the genus, and is also the most 



