36 



SHELL GALLEEY. 



Cases 148- 

 149. 



Cases 150- 

 153. 



The SpondylidcB, or Thorny Oysters, closely resemble the Scallops, 

 but the shells are more spiny, heavier, united by interlocking teeth, 

 and they are attached by ore valve to rocks, corals, etc. Many of the 

 species are very brightly coloured ; and from the fact that small quanti- 

 ties of water are sometimes enclosed in cavities in the inner layer of 

 the shell, they have been called " Water-Clams " or " Water Spondyli." 



The Scallops or Fan-shells {PecHnidce) are well known for their 

 beautiful colours, sculpture, and excellent flavour. The animal has 



Fig 29 



Cases 153- 

 204. 



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. 



a distinct foot, which is not, however, used as a locomotive organ, 

 but employed in spinning a byssus of attachment when required. 

 The young Pectens dart through the water by opening and suddenly 

 closing their valves. The species are very numerous, world-wide in 

 their distribution, and may be found at depths from a few to three 

 thousand fathoms. 



EULAMELLIBEANCHIA. (Fig. 25, C.) 



In this order the gills have interfilamentar and interlamellar 

 vascular junctions, and there are generally two adductor muscles. 



