94 BRITISH FRESHWATER RHIZOPODA. 



be confused, it is distinguished by its usually smaller 

 test, with a smooth outline and more elongate form, 

 but intermediate forms not unfrequently occur. 



The identity of Trinema linear e with Ehrenberg's 

 Arcella liyalina does not admit of doubt. Their tests 

 are precisely alike in shape, size, and smooth hyaline 

 appearance, and the fact that Ehrenberg appears to 

 have found this species more common than T. enchelys 

 is corroborative evidence. He seems to have found 

 it nearly everywhere. 



We cannot, however, adopt his specific name, as in 

 his ' Infusionthierchen ' (1838) he had called the 

 species we now know as Lecythium liyalinum, Arcella 

 (?) hyalina. 



3. Trinema complanatum Penard. 

 (Plate XL VIII, figs. 4 and 5.) 



1 Arcella nidus-pendulus 

 EHRENBERG in Ahb. Akad. Berlin, 1841, i, pp. 410, 441, pi. iii, i, f . 48 ; 



op. cit. 1871 (1872), pp. 235, 264. 

 Trinema acinus 

 LEIDY (pars) Freshw. Rhiz. N. Amer. (1879) pp. 226-229, pi. xxxix, 



ff. 32, 33, 41, 47, 48, 61-63. 

 Trinema complanatum 

 PENARD in Mem. Soc. Geneve, XXXI, i (1890), n, p. 187, pi. x, ff. 



1-4; in Jahrb. nassau. Yer. Naturk. XLIII (1890), p. 72 ; in Amer. 



Natur. XXY (1891), p. 1071; Faune Rhiz. Leman (1892), pp. 528- 



529, 2 figs. ; in Arch. Protist. II (1902), p. 271 ; Sarcodines in Cat. 



Invert. Suisse (1905), pp. 109-110; in Arch. Protist. IX (1909), 



p. 265 ; in Brit. Antarct. Exped. I (1911), pp. 221, 253. 

 AVERINTZEFF in Trudui S.-Peterb. Obshch. XXXYI, n (1906), pp. 



310-311 ; in Zool. Anzeig. XXXI, (1907), p. 246. 

 SCHOUTEDEN in Ann. Biol. lacustre, I (1906), p. 371, f. 50. 

 EVANS in Proc. R. Phys. Soc. Edinb. XYII (1907), table 1. 

 COCKERELL in Univ. Colorado Stud. YI (1908), p. 30. 

 HEINIS in Arch. Hydrobiol. Y (1910), p. 110. 

 HOPKINSON in Irish Natur. 1910, p. 3. 

 BROWN in Ann. Scott. Nat. Hist. 1911, pp. 229, 230 ; in Naturalist, 



1912, p. 181 ; in Scott. Natur. 1912, p. 112 ; 1913. pp. 208, 210. 

 WAILES & PENARD in Proc. R. Irish Acad. XXXI, LXV (1911), pp. 



19, 60. 



EDMONDSON in Univ. Colorado Stud. IX (1912), p. 69. 

 WAILES in Scott. Natur. 1912, p. 61 ; in Jrn. Linn. Soc., Zool. XXXII 



(1912), pp. 126, 152 ; loc. cit. (1913), p. 213 ; in Murray's Nat, Hist. 



Bolivia and Peru (1913), pp. 32, 40; in Naturalist, 1913, p. 148. 



Test small, hyaline, formed of circular, imbricated, 



