54 BRITISH -B'EESHWATER EHIZOPODA. 



Ges. Wiss. 1881 (1882), p. 227; Geeeff in Sitzber. Ges. 

 Nat. Marburg, 1888, -p. 107 ; Haevey in Amer. Natur. 

 XXII (1888), p. 72 (as ascula) ; Ceetes in Mission scient. 

 Cap. Horn, A"! (1889), 3, Prot., p. 13; Penaed (pars) in 

 Mem. Soc. Genfeve, XXXI (1890), 2, p. 148, t. iv, ff. 92, 

 94-96, 98, 99; in Amer. Natur. XXV (1893), p. 1071 ? ; 

 in Arch. Sci. nat. (4) VII (1899), p. 268; Paune Phiz. 

 Leman (1902), p. 296, ff. 1-4 (p. 297) ; and in Jrn. E. 

 Micr. Soc. 1907, p. 277; Cash in Tr. Mauch. Micr. Soc. 

 1891 (1892), p. 48; Levander in Acta Soc. Fauna Fenn. 

 XII (1894), 2, p. 18 ; and op. cif. XX (1901), 8, pp. 8, 10 ; 

 Daday in Termesz. Fiizetek, XXI (1898), Suppl. pp. 6, 9 ; 

 Eyfeeth Naturgesch. mikr. Siisswass. ed. 3 (1900), p. 

 263; LAGHUHEiMinPorl:. Geol. P5ren. Stockholm, XXIII, 

 6 (1901), p. 472; Aveeintzev inTrudui S.-Peterb. Obshch. 

 XXXVI (1906), 2, p. 181; ScHOUTEDEN in Ann. Biol. 

 Lacustre, I, 3 (1906), pp. 341, 344; Mueeay in Ann. 

 Scott. Nat. Hist. 1907, p. 94. 



Test hemispLerical, with a slightly concave base, the 

 crown regularly arched, incriisted with fine sandy or 

 muddy particles, opaque; the mouth (interiorly situ- 

 ated) triangular or irregularly trilobed, or roughly 

 quadrangular, and never invaginated as in Arcella. 

 Nucleus single; pseudopodia normal [?]. 



TJimeuHidHs : Diameter of base about 90 /x; elevation 

 of crown 40-45 /u.. 



In marshy places ; also in tufts of moss and liver- 

 wort growing on moist rocks ; and in shady woods ; 

 frequent. 



The form with triangular mouth is probably the one 

 most frequent with us. Occasionally in Splunjnum the 

 mouth is irregularly quadrate. In no case is the rim 

 inverted as in some examples figured by Leidy, which 

 belong to Ceidrojii/.vis. 



23. Difflugia constricta (Ehrenb.) Leidy. 



(Plate XIX, figs. 14-20; PL XXII, figs. 12-14; 



and figs. 66-69 in text.) 



Arcella constricta Ehkenbeeg in Abli. Akad. "VA'iss. Berlin, 

 1841, ]i. 410, t. iv, f. 35, and t. v, f. 1; op. cif. 1871 



