9l5 BRITISH FRESHWATER RHIZOPODA. 



Genus 40. CORYTHION Taranek, 1881. 



Arcella (pars) EHRENBERG in Abh. Akad. Berlin, 1841, p. 410. 

 ? Euglypha (pars) PERTY Kenntn. kleinst. Lebensf. (1852), 



p. 187. 

 Trinema (pars) LEIDY Freshw. Khiz. N. Amer. (1879), 



p. 226. 

 Corythion TABANEK in Sitzb. bohm. Ges. Wiss. 1881, p. 232. 



Test small, hyaline, composed of small non-imbri- 

 cated, oval, silicious plates ; compressed ; in broad 

 view sub-circular to oviform ; transverse section ellip- 

 tical ; aperture sub-terminal, ventral, or oblique, 

 circular or oval; plasma colourless, granular, only 

 partially filling the test ; nucleus placed posteriorly ; 

 contractile vesicles one or two in number ; pseudo- 

 podia filose, more or less numerous, straight, radiating. 



SYNOPSIS OF THE BRITISH SPECIES. 



Test sub-circular or ovoid; transverse section oval or 

 lenticular ; aperture ventral. (1) C. dubium. 



Test ovoid ; transverse section oval ; aperture sub-terminal, 

 oblique. (2) C. pulchellum. 



1. Corythion dubium Taranek. 

 (Plate XLVIII, figs. 6-18.) 



Arcella constricta 



EHRENBERG (pars) in Abh. Akad. Berlin, 1841, I, p. 410, pi. iv, i, 



f. 35 ; Mikrogeol. (1854), pi. xxxix, ill, f. 3. 

 Arcella disphaera 



EHRENBERG (pars) in Abh. Akad. Berlin, 1841, i, p. 410, pi. iv, 11, 



f. 12. 



Trinema acinus 

 LEIDY (pars) in Fresh w. Rhiz. N. Amer. (1879), pp. 226-228, pi. xxxix, 



ff. 10-13, 18. 

 Corythion dubium 

 TARANEK in Sitzb. bohm. Ges. Wiss. 1881, p. 232, f. 3 ; in Abh. bohm. 



Ges. Wiss. (6) XI (1882), pp. 31, 43-46, 65, pi. iii, ff. 17-24. 

 PENARD in Mem. Soc. Geneve, XXXI, i (1890), u, pp. 188-189, pi. xi, 

 ff. 18-26; in Amer. Natur. XXV (1891), pp. 1071, 1079; Faune 

 Rhiz. Leman (1902), pp. 531-532, 5 figs. ; in Arch. Protist. II (1903), 

 p. 272 ; op. cit. IX (1909), p. 265 ; Sarcodines in Cat. Invert. Suisse 

 (1905), pp. 110-111 ; in Brit. Antarct. Exped. I (1911), pp. 220, 229, 

 pi. xxii, f . 3 ; in Deux, exped. antarct. franc;. (1911), pp, 4, 6. 



