CONCHIFEEA. 461 



Galeomma, Tui'ton. 



Synonyms, Hiatella, Costa (not Daud.) ; Parttenopea, Scacclii 

 (not Fabr). 



Type, G. Turtoni, PI. XIX., Fig. 15. {Oalee, weasel, omma, 

 eye.) 



Shell tMn, 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 Oaleomma spins a byssus, but breaks from its mooring 

 at will and creeps about like a snail, spreading out its valves 

 nearly flat. (Clarke.) 



Bistribution, 14 species. Britain, Mediterranean, Maui-itius, 

 Pacific. 



Fossil, 1 species. Pliocene — . . Sicily. 



Family XII. — Cycladid^. 



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 

 hmall 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 Cyrence 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, Bruguiere. 



Etymology, JcuJclas, orbicular. 

 Type, C. Cornea. PL XIX., Fig. 17. 



Synonyms, Sphcerium, Scop. Pisum, Muhlf. (not L.) Miis- 

 3ulium, Link. 



