ARCELLA MITRATA. 125 



prominent folds ; base rounded at the border, inverted, 

 concavely infundibuliform, mouth circular, crenu- 

 lated, mostly everted within the inverted funnel. 

 Plasma-body spheroidal, usually connected with the 

 mouth by a cylindrical neck, and attached by threads 

 of endoplasm to the interior of the test. Pseudopods 

 variable in number, up to half a dozen or more. 



Dimensions: Height of test 1 00-145 /x; diameter 

 1 00-152 ju (West). 



Amongst Sphagnum and Utricularia minor, Cocket 

 Moss, Giggles wick, West Yorkshire; and in Sphagnum- 

 pools on Moel Siabod, North Wales (G. S. West). 



Professor Leidy (whose description we quote) found 

 this species abundant in some parts of Pennsylvania, 

 but in Europe it seems very scarce. West (loc. tit.) 

 remarks : " The mouth of the shell of this rhizopod is 

 inturned into the cavity of the shell, forming a short, 

 broad, tube-like mouth. Leidy figures the pseudo- 

 podia as arising from the body-protoplasm at the 

 inner end of the tube ; but in all the living forms 

 observed, a ventral column of protoplasm passed from 

 the body-protoplasm into this tube, completely filling 

 it to the outer end. The pseudopodia then arose from 

 the extreme ventral surface of this mass of protoplasm 

 in the tube." 



4. Arcella dentata Ehrenberg. 

 (Plate XV, figs. 7 and 8 ; and figs. 21-23 in text.) 



Arcella dentata EHRENBERG in Abth. K. Akad. Wiss. Berlin, 

 1830 (1832), pp. 31, 40, 71; op. cit. 1831 (1832), p. 90; 

 Infus. (1838), p. 134, t. ix, f. vii; and in Ber. K. Akad. 

 Wiss. Berlin, 1853, p. 255; PEITCHARD Hist. Infus. (1842), 

 p. 170; new ed. (1852), p. 211; and ed. 4 (1861), p. 155; 

 EYMER JONES in Todd's Cycl. Anat. IV (1847), p. 10, f. 7, 

 no. 2 ; BAILEY in Smithson. Contrib. II (1851), art. 8, 

 passim; PERTY in Mitth. naturf. Ges. Bern. 1849, p. 163, 

 and Kenritn. kleinst. Lebensf. (1852), p. 186; LEIDY in 

 Proc. Acad. Nat. Sci. Phil. 1874, p. 14; op. cit. 1876, 



