48 The Shell-Collector’s Handbook. 
‘\ 
teeth very small and difficult to see. Animal milk-white. 
Length of shell 3 inch; width 2ths inch; thickness 4 
inch. 
Habitat.—Ponds and rivers. Local. 
SPHARIUM LACUSTRE, MULL. 
SHELL subrhomboidal, rounded or elliptical, much com- 
pressed, thin, yellowish-white, or ashy in colour, regularly 
striate concentrically ; umbones central, narrow, promi- 
nent, and capped with the nucleus of the shell ; ligament 
short, slightly visible externally ; muscular impressions in- 
distinct ; hinge strong; teeth as in the other species, but 
smaller and shorter in proportion. Body whitish, or 
slightly rose-coloured; siphons elongated, the branchial 
one being cylindrical and truncated at its orifice. Length 
of shell 4 lines, width 3 lines; thickness 13 lines. 
Habitat.—Ponds and canals. 
v. Brochoniana (Bowrg.): Shell much larger and 
flatter; umbones, smaller and not so well pronounced. (=. 
Brochonianum Bourguignat, Monogr, Spher, p. 20, pl. 3, f. 
2S); 
v. rotunda (Jeff.): Shell rounder and flatter; epidermis 
yellowish-green. (B.C. vol. i,, p. ii.) 
v. Ryckholtii (Norm.): Shell small, triangular, and 
globular; umbones very pronounced. (=C. Ryckholti, 
Norm. Cyel. p. vii., f. v., vi). 
