74-75. 



78-81. 



20 SHELL GALLEKY. 



Cases The family of lluricidce, or " Eock-shells," is another extensive 



70-76. group, containing many very handsome and peculiar forms. The 

 animals of this family have a long protractile proboscis, at the end 

 of which is the spiny tongue (radula). The true Murices produce at 

 intervals ribs or varices, which in some species are ornamented with 

 long spines or foliations, and which indicate periods of growth, but 

 of what duration we do not know. They are all carnivorous, 

 feeding chiefly on other Mollusca, boring through the shells of 

 bivalves with their spiny tongue, and slowly devouring the unfor- 

 tunate inhabitant piecemeal. From certain species of Miirex {M. 

 orandaris, &c.) found in the Mediterranean, the ancients manufac- 

 tured the celebrated Tyrian purple dye. 



Cases The " Purples " {Purpura) are found between tide-marks all 



over the world. Magilus, belonging to the family CoralMopliilidm 

 (Case 77), is found among coral-reefs in tropical seas, and has the 

 remarkable habit of lengthening the aperture of its shell into an 

 elongate tube, in order to keep pace with the growth of the coral, 

 and to prevent its being overgrown and killed. 



Cases The "Volutes" (Volutidce) are a group of shells also much 



sought after by shell-collectors. Some of these attain to a very large 

 size, the animals inhabiting them being enormous. The Boat- 

 shells {Cymld) and Melons {Cymhium) are ovo-viviparous, the young 

 being carried about by the parent until they are an inch in length. 

 Volutes are found chiefly in the warmer parts of the Atlantic and 

 Indo-Pacific Oceans, and occur in the greatest variety on the coasts 

 of Australia. 



The Olives (OJm'dm) are common in most tropical seas, and are 

 remarkable for their beautiful polish and various patterns of colour- 

 ing. In structure and form they are very similar to each other. 

 They burrow in sand in quest of bivalves for food, and some species 

 are said to have the power of swimming by expanding the lobes of 

 the foot. 



Case 84. The Harps {Harpidce) form a small well-marked group, of which 



probably nearly all the existing species have been discovered. The 

 animals inhabiting these beautiful shells are also brightly coloured. 

 They have the remarkable power of casting off a portion of the foot 

 when disturbed. The species are known from the Indo-Pacific Ocean, 

 the west coast of Central America, and West Africa. 



Cases The next family, the " Slit-lips " (Pleurofomidce), consists of 



very numerous species, over a thousand living forms having been 

 discovered, and almost as many fossil species from Cretaceous and 



81-83. 



85-87. 



