(13) 
Order II. CONCHULINA. 
Family 1. AkcELLipa. 
$8 A. ARCELLINA. 
1. Arcella vulgaris var. hemispherica (Perty) 
var. nov. 
(Plate LIX, fig. 5, and fig. 161 in text.) 
Arcella hemispherica 
Prrty Kenntn. kleinst. Lebensf. (1852), p. 186, pl. ix, f. 5. 
PENARD in Mém. Soc. Genéve, XXXI, 2 (1890), p. 153, pl. v. ff. 93- 
95; in Rev. Suisse Zool. IX (1901), p. 237; Faune Rhiz. Léman 
(1902), p. 400, 4 figs.; in Proc. R. Soc. Edinb. XXV, 8 (1905), 
pp. 593, 596 ; Sarcodinés in Cat. Invert. Suisse (1905), pp. 78-79. 
GopDET in Bull. Soc. Neuchatel. XXVIII (1899), p. 78. 
Waites & PENARD in Proc. R. Irish Acad. XXXI, txv (1911), p. 65. 
Waites in Jrn. Linn. Soc. Zool. XX XIT (1912), pp. 123, 130. 
Test smaller than in the type, nearly hemispherical 
in side view, the basal diaphragm forming nearly a 
right angle with the circular dome as seen in vertical 
section ; the base concave with a central circular 
Fie. 161.—Arcella vulgaris var. kemispherica. Side view. x 250. 
(After Cash.) 
orifice usually everted ; plasma, nuclei, and contractile 
vesicles as in the type. 
Diameter of test usually 40 » to 50 pw, sometimes 
less. 
Habitat— Ponds and ditches. Generally distributed. 
Described by Perty under a specific name, this 
variety is included in Vol. I, p. 120, by Cash among 
the synonyms of A. vulgaris, but it seems to deserve 
at least varietal rank. 
