LAMELLIBRANCHIA. 
37 
hatched outside the parent shell. Oysters of different kinds are 
found on nearly every shore. The gigantic 0. gigas is said to 
grow to the length of three feet in the Bay of Taichou, Japan, 
where it is commonly eaten. About two hundred fossil species have 
already been described. 
The Spondylitica, or Thorny Oysters, closely resemble the Scallops, Cases 154- 
but the shells are more spiny, heavier, united by interlocking teeth, 
and one of the valves is attached to rocks, corals, etc. Many of the 
species are very brightly coloured ; and from the fact that small 
Fig. 30. 
356. 
Common Edible Oyster (Ostrea edulis). 
a, labial palpi ; h, gills ; c, mantle ; d, junction of the two folds of the mantle ; 
e, large adductor muscle ; /, the shell. 
quantities of water are sometimes enclosed in cavities in the inner 
layer of the shell, they have been called " Water-Clams " or " Water 
Spondyli." 
The Limas (Limida) are very like the Pectens, but the inner Case 156. 
edge of their mantle is fringed with very long thread-like filaments. 
The shells are always white, generally more or less oblique, • and 
radiately ridged. They appear to be found in most seas, and either 
swim about freely like the young Scallops by flapping their valves 
