AMPHITREMA PLAVUM. 149 



cially in upland districts. The average size of British 

 individuals (55-70 ju, in length) appears to be greater 

 than that of the Swiss (45-55 )u,: Penard), but in the 

 United States the size is about the same as in the 

 British Isles. 



A noticeable peculiarity of this species is the 

 apparent tendency of individuals to divide into halves 

 transversely {vide Penard, ' Faune Ehiz. Leman '). 

 At Leckby Carr near York, where' this species occurs 

 numerously, many individuals as shown in Plate LVI, 

 fig. 4, were seen, but in no case had the division pro- 

 ceeded beyond the depicted stage. 



In Mayo this species was found by Penard contain- 

 ing spherical blue-green algae (4 /a dia.) which were 

 not Ghlorella vulgaris (Beyerinck), the species usually 

 found living symbiotically with Rhizopoda. 



2. Amphitrema wrightianum Archer. 

 (Plate LVII, figs. 6-8.) 



(Allied to Actinophrys or Acineta 



Beightwbll Fauna Infus. E. Norfolk (1848), p. 24, pi. xi, f. 3.) 

 Amphitrema wrightiamim 



Aechbe in Qrt. Jrn. Micr. Soi. (n. s.) IX (1869), p. 397, pi. xx, ff. 



4, 5 ; op. cit. (N. s.) X (1870), pp. 20-21, 122, pi. xx, fE. 4, .5 ; (n. s.) 



XYI (1876), p. 341 ; in Proc. Dtibl. Micr. Club, I, 5 (1872), pp. 



355-356, 390-391, pi. xiii, fE. 4, 5 ; op. cit. Ill, 2 (1878), p. 132. 

 BuETSCHLi in Bronn's TMerreiohs, 1, 1 (1880), pi. iv, f. 3. 

 Lankestbb in Encyol. Brit., ed. 9, XIX (1885), p. 16, f. ix (11); 



in Zool. Art. contrib. Bncycl. Brit. (1891), p. 16, f. ix (11). 

 Blochmann Mikr. Tliierw. Siisswass. (1886), p. 16 ; ed. 2 (1895), 



p. 20. 

 Dblagb & Hbeouard Traite Zool. concrete, I (1896), p. 116, f . 154, 

 Wbst in Jrn. Linn. Soc, Zool. XXVIII (1901), p. 332. 

 Chapman Foraminifera (1902), p. 71, pi. i, f. p. 

 Pbhard Panne RMz. Leman (1902), pp. 539-540, 3 figs. ; Sarcodines 



in Oat. Invert. Suisse (1905), p. 113. 

 AvBEiNTZBPP in Trudui S.-Peterb. Obslicli. XXXVI, ii (1906), p. 95, 



pi. ii, f. 37 ; pp. 320-321 ; in Ann. Biol, lacustre, I (1906), p. 324. 

 ScHOUTBDBN in Ann. Biol, lacustre, I (1906), p. 373. 

 Evans in Proc. B. Pliys. Soc. Edinb. XVII (1907), table 1. 

 Hbinis in Arch. Hydrobiol. V (1907), p. 111. 

 HOPKINSON in Irish Natur. 1910, p. 3. 

 Bbown in Jrn. Linn. Soc, Zool. XXXII (1911), p. 84. 

 Haetog in Encycl. Brit., ed. 11, XXIIl (1911), p. 248, f. 7 (10). 

 Wailbs & Pbnakd in Proc. R. Irish Acad. XXXI, lxv (1911), pp. 



14, 20, 61. 



