CONCHIFERA. 461 
GALEOMMA, Turton. 
Synonyms, Hiatella, Costa (not Daud.); Parthenopea, Scacchi 
(not Fabr). 
Type, G. Turtoni, Pl. XIX., Fig. 15. (Galee, weasel, omma, 
eye.) 
Shell thin, oval, equilateral, gaping widely below; invested 
with a thick, fibrous epidermis; beaks minute; ligament 
internal; teeth 0.1. 
Animal with the mantle-lobes united behind and _ pierced 
with one siphonal orifice, margins double, the inner with a row 
of eye-like tubercles; gills large, sub-equal, united behind ; 
lips large, palpi lanceolate, plaited; foot long, compressed, 
with a narrow flat sole. 
The Galeomma spins a byssus, but breaks from its mooring 
at will and creeps about like a snail, spreading out its valves 
nearly flat. (Clarke.) 
Distribution, 14 species. Britain, Mediterranean, Mauritius, 
Pacific. 
Fossil, 1 species. Pliocene—. . Sicily. 
FAMILY XII.—CYcLADIDA. 
Shell sub-orbicular, closed; ligament external; epidermis 
thick, horny; umbones of aged shells eroded; hinge with car- 
dinal and lateral teeth; pallial line simple, or with a very 
small inflection. 
Animal with mantle open in front, margins plain; siphons 
(1 or 2) more or less united, orifices usually plain; gills 2 on 
each side, large unequal, united posteriorly ; palpi lanceolate ; 
foot large, tongue-shaped. 
All the shells of this family were formerly included in the 
genus Cyclas, a name now retained for the small species inha- 
biting the rivers of the north temperate zone; the Cyrene are 
found in warmer regions, on the shores of creeks and in brackish 
water, where they are gregarious, burying vertically in the 
mud, and often associated with members of marine genera. 
CycLas, Bruguiére. 
Etymology, kuklas, orbicular. 
Type, C. Cornea. Pl. XIX., Fig. 17. 
Synonyms, Spherium, Scop. Pisum, Muhlf. (not L.) Mus- 
sulium, Link, 
