94 BRITISH JTRBSHWATER 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 lineare with Bhrenberg's 

 Arcella hyalina 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 ' Inf usionthierchen ' (1838) he had called the 

 species we now know as Lecythium hyalinum, Arcella 

 (?) hyalina. 



3. Trinema complanatum Penard. 

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



? Arcella nidus-pendulus 

 Eheenbeeg in Alib. Akad. Berlin, 1841, I, pp. 410, 441, pi. iii, i, f. 48 ; 



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

 Trinema acinus 

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



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

 Trinema complanatum 

 Pbnaed in Mem. Soo. Geneve, XXXI, i (1890), ii, p. 187, pi. x, ff. 



1-4; in Jahrb. nassan. 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 ; Saroodines in Oat. 



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



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

 AvBEiNTZBPP in Trudui S.-Peterb. Obshch. XXXVI, II (1906), pp. 



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

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

 Evans in Proc. R. Phys. Soc. Edinb. XVII (1907), table 1. 

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

 Hbinis 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 & Penaed in Proc. R. Irish Acad. XXXI, lxv (1911), pp. 



19,60. 

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

 Wailbs in Scott. Natur. 1912, p. 61 ; in Jm. Linn. Soc, Zool. XXXII 



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



Bolivia and Peni (1913), pp. 32, 40; in Natui-alist, 1913, p. 148. 



Test small, hyaline, formed of circular, imbricated, 



