314 MR. G. 8. WEST ON SOME BRITISH 
Diameter of shell 42 «4; diameter of mouth of shell 34 p; 
length of spines 23-29 p. 
Wicken Fen, Cambridgeshire: July 1899, amongst Chara 
hispida. 
The thin shell and the extremely long, delicate spines readily 
distinguish this species from C. vestitum, Archer. The spines 
are also more numerous than in the latter species, and the mouth 
of the shell is comparatively broader than in any specimen of 
C. vestitum I have seen. The pseudopodia are also thicker and 
‘more expansive, and the refractive globules from the body of 
the animal often pass into them. No green colouring-matter 
was obtained in any of the examples. 
Gen. ArceLLa, Hhrenb. 
13. ARCELLA VULGARIS, Hhrenb. Abhand. Akad. Wiss. Berlin, 
1830, pp. 40, 53, ete. t. i. f. vi; Infus. 1838, p. 183, t. ix. f. v; 
Carter, in Ann. Mag. Nat. Hist. xviii. 1856, p. 128, t. vii. f. 79 ; 
1864, xiii. p. 30, t. 11. f. 14.—A. hemispherica, Perty, 1852. 
Arcellina vulgaris, Carter, 1856. 
Generally distributed throughout the British Islands. 
Var. GipBosa.—Arcella vulgaris, Leidy, Freshw. Rhiz. N. 
Amer. 1879, t. xxvi. ff. 23-24.—Arcella gibbosa, Penard, in Mém. 
Soc. de Phys. et d’Hist. Nat. de Genéve, 1890, tome xxxi. no. 2, 
p- 155, t. v. ff. 96-99, t. vi. f. 1. 
The convex surface of the shell faceted, the facets being 
circular depressions which fade away towards the edges of the 
shell. Shell dark brown in colour, sometimes, nearly black. 
In bogs, New Forest, Hants. In pools, Llangelynin, near 
Conway, N. Wales. Bog about two miles south of Clapham, 
W. Yorkshire. 
From the last-named locality the specimens were very large, 
exceeding in dimensions any forms of the species I have yet 
come across. The diameter of the shell was in some cases as 
much as 240 p. 
14. ARcELLA DIscoipEs, Hhrenb. Monatsb. Akad. Wiss. Berlin, 
1843, p. 189; Leidy, Freshw. Rhiz. N. Amer. 1879, p. 1738, 
t. xxvii. ff. 14-38. 
Widely distributed, but not so abundant as A. vulgaris. At 
2200 tt. on Glyder Fach, N. Wales. ; 
