296 MANUAL OF THE MOLLUSCA. 



LEPTON, Turton. 



Etym. Lepton, a minute piece of money (from leptos, thin). 



Syn. ? Solecardia (eburnea) Conrad, L. California. 



Type, L. squamosum. PI. XIX. fig. 34. Fig. 215. 



Shell sub-orbicu]ar, compressed, smooth, or shagreened, a little opened at 

 the ends and longest behind; hinge-teeth 0.1 or 1.1. in front of an angular 

 cartilage notch; lateral teeth 2.2 and 1.1. 



Animal with the mantle (m] open in 

 front, extending beyond the shell, and 

 bearing a fringe of filaments, of which 

 one in front () is very large; siphon 

 (s) single ; gills 2 on each side, separate; 

 foot (f) thick, tapering, heeled and 

 grooved, forming a sole or creeping disk. 

 (Alder.} Fig. 215. Lepton. 



Distr. 3 sp. U. S. Brit. Spain. Laminarian and Coralline Zones. 



Fossil, Miocene . U. S. Brit. 



GALEOMMA, Turton. 



Syn. Hiatella, Costa (not Daud.) ; Parthenopea, Scacchi (not Fabr.) 



Type, G. Turtoni, PI. 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 1 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.} 



Distr. 3 sp. Brit. Medit. Mauritius, Pacific. 



Fossil, Pliocene . Sicily. 



FAMILY XI. CYCLADID^E. 



Shell sub-orbicular, closed ; ligament external ; epidermis thick, horny ; 

 umbones of aged shells eroded ; hinge with cardinal 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 inhabiting the rivers of the north 

 temperate zone ; the Cyrena 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. 



