CH. IX THE COLOURS AND PIGMENTS OF MOLLUSCA 185 



dent with the most gorgeous colours. This giant 

 clam occurs freely among the corals of the Australian 

 Barrier Reef, and during life the valves gape widely, 

 disclosing the frilled mantle -folds which give the 

 species its popular name. These are often coloured 

 with shades of blue varying from " palest turquoise 

 to the richest ultramarine," or are green variegated 

 with spots and markings of black. Sometimes the 

 ground colour is purple or rich brown spotted and 

 streaked with bright blue or green. The shell in 

 this clam is a pale yellow, and the organisms are 

 exceedingly conspicuous on the reefs. In many 

 Molluscs the pigments of the mantle are confined to 

 special spots, as in the case of the simple " eyes " 

 of many Lamellibranchs, but cases of uniformly 

 diffused colour are far from uncommon. The 

 delicate pink colouring of the fringed mantle-folds of 

 Lima is familiar to all those who have done coast 

 dredging. In Patella vulgata, the common limpet, 

 the dorsal body wall is of a deep blue-black colour, 

 while in the little tortoise-shell limpet {Acmcea 

 testudinalis), common on Scotch coasts, the same 

 region is a delicate blue-green. In the shell-less 

 Gasteropods, such as the sea-slugs {Doris, etc.) and 

 the terrestrial slugs Limax, etc., the whole of the body 

 wall is usually coloured, often with bright pigments, 

 but this is much less inexplicable than the occurrence 

 in the mantle of shelled forms of bright pigments 

 having no obvious relation to the pigments of the 

 shell. 



As to the colours of the Cephalopoda there is 

 little need either for description or eulogy ; most 

 people must have seen and admired the lovely 



