Heart-Cockle and FresJi-zvater Cockle 103 



oval, unequal-sided, white, deeply tinged with red 

 towards the upper margin, and covered by a yellowish 

 epidermis. There are two lateral teeth in each valve, 

 but in the left valve there is in addition a small 

 cardinal. The mantle does not extend so much be- 

 yond the shell as in Kellia, but in front it forms a 

 protuberant incurrent tube. The excurrent orifice is 

 not seen beyond the shell margin. The long, tongue- 

 shaped foot is used for similar purposes as in the 

 last-named species, and a byssus of less simple 

 character moors it to rock-crevices, to corallines and 

 other seaweeds, chiefly between tide-marks, all round 

 our coasts. It is a species that retains its eggs until 

 they are hatched. These are produced in batches of 

 from 12 to 20, and when sufficiently developed the 

 fry are shot into the world of waters through what 

 ordinarily serves as the incurrent siphon. 



The Coin - shells (Lepton), so - called from their 

 resemblance to a small coin (lepton), are represented 

 by five native species. They differ in several respects 

 from the creatures just described. The shell is more 

 liberally provided with hinge-teeth, there being a 

 cardinal and two laterals in each valve. The mantle, 

 which is fringed with long tentacles, protrudes nearly 

 all round, and the foot can be flattened in such manner 

 that it resembles the foot of a snail, and is 

 used in similar fashion. The Scaly Coin- 

 shell {L. squamiosmn) is almost square and 

 flat, its substance thin almost to transpar- 

 ency, glossy, and white. It is finely ribbed 

 in two directions, the spaces left between 

 the network thus formed giving the surface the ap- 

 pearance of being minutely pitted. Inside the shell is 



