124 ERESH-WATEE RIIIZOPODS 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 Ath 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 Ath of an inch, and the mouth was Ath of an inch 

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

 Ath of an inch broad, Ath of an inch thick, and the mouth Ath of an inch 

 wide. The spines of the fundus reach a length of Ath of an inch. 



DIFFLUGIA SPIRALIS. 



Plate XIX, figs. 1-23. 



Difflugia. Lcclcrc: M<5m. Mus. Hist. Nat. 1815, ii, 474, pi. 17, figs. 1 and 4. 



Difflugia spiralis. -Ebrenberg: Monatsb. d. Berlin. Akad. d. Wissens. 1840, 199; Abliand. Akad. Wissens. 

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

 Fresenius: Abliand. Senckenb. Natnrf. Gesells. ii, 1856-8, 224, Taf. xii, Fig. 37-42.— Pritcbard: 

 History of Infusoria, 1861, 553.— Carter: An. Mag. Nat. Hist, xiii, 1804, 18, pi. i, fig. 9.— 

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



Leequcreusia jurassica. Scblumberger : An. Sc. Nat. 1845, 255. 



Difflugia proteiformis, moustrosa. Pcrty : Kenntniss kleinster Lebensfornicn, 1852, 187, 214, Taf. viii, Fig. 22. 



Difflugia Helix. Cobn : Zeitscb. f. -wissens. Zoologie, 1853, 261. 



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



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



Difflugia jn-oteiformis, subspecies D. mitriformis, var. fi. D. spiralis. Wallieb: An. Mag. Nat. Hist. 1864, 

 xiii, 1834, 240, pi. xvi, figs. 24, 25. 



D. Corticella spiralis. Ebrenberg: Abb. 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. 



fee.— 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 



