150 BRITISH FRESHWATER RHIZOPODA. 



WAILES in Scott. Natur. 1912, p. 60 ; in Jrn. Linn. Soc., Zool. XXXII 



(1912), pp. 126, 153 ; in Naturalist, 1913, p. 148. 

 SCHMIDT in Avch. Protist. XXIX (1913), pp. 222, 226. 

 Amphitrema wrightiana 



AVERINTZEFF in Arch. Protist. YIII (1906), p. 118. 

 BUTLER in. Brit. Assoc. Handb. Dublin (1908), p. 218. 



Test composed of a fine membranous envelope, 

 elliptical, compressed, covered with plates or ex- 

 traneous particles; in narrow side view oblong or 

 elongate-oval; transverse section oval; apertures small, 

 oval, placed centrally at each end and provided with 

 short tube-like external collars ; plasma colourless, 

 granular, not completely filling the test, usually 

 containing Chlorella-cells living symbiotically ; nucleus 

 large, containing several nucleoles, placed centrally ; 

 a single contractile vesicle usually present; pseudo- 

 podia attenuated, straight, sparsely branched, and 

 radiating. 



Length 61-95 /A ; breadth 43-64 p ; thickness from 

 one half to three fifths of the breadth ; aperture 6^10 p. 

 in width ; length of collar 3-4 p. 



Habitat. Sphagnum. 



ENGLAND. Westmorland ; N. Yorkshire ; Norfolk 

 (Bright well) i Hampshire; Isle of Wight; Devonshire; 

 Cornwall. 



WALES. Carnarvonshire and Merionethshire (Cask). 



SCOTLAND. Shetland Islands ; Perthshire (Cash, 

 Brown) ; Midlothian (Cash) ; Dumfriesshire; Wigtown- 

 shire (Brown). 



IRELAND. Clare Island and mainland, Mayo ; West- 

 meath, Gal way, Co. Dublin, Wicklow, and Kerry ! 

 (Archer). 



Although not nearly so plentiful as A. flavum, this 

 species is often associated with it; the particles which 

 thickly encrust the membranous test usually consist 

 of silicious grains and diatom-frustules ; they are often 

 so thickly aggregated around the apertures that the 

 projecting collars are discerned with difficulty ; the 

 extremities of the collars are often slightly expanded. 



