UX/ VALVE MOLLUSC A. 455 



The shells of the less marked species are frequently used in India as 

 lime for making mortar, under the name of Chunam. 



Our space only permits us to mention, among the more curious 

 species, Cassis canaliciilata (Fig. 281), two varieties of Cassis Mada- 

 gascariensis (Figs. 282 and 283), and the curious Cassis Zebra 

 (Lam.), or Zebra-marked Casque (Fig. 284). 



The Purpuras have a classical name and history, having furnished 

 the Greeks and Romans with the brilliant purple colouring matter 

 which was reserved for the mantles of patricians and princes. The 

 genus Purpura is characterised as possessing an oval shell, thick 

 pointed, with short conical spiral, as in Purpura lapillus (Fig. 285). 

 In some it is tubercular or angular, the last turn of the spiral being 

 larger than all the others put together. The opening is dilated, ter- 

 minating at its lower extremity in an oblique notch. The columellar 

 edge is smooth, often terrainating in a point ; the right edge often 

 digitate, thick internally, and folded or rippled. 



The animal presents a large head, furnished with two swollen 

 conical tentacles, close together, and bearing an eye towards the 

 middle of their external side. Its loot is large, bilobate in front, 

 with a semicircular horny operculum. 



The species of Purpura inhabit the clefts of rocks in marine 

 regions covered with alg?e. On occasions they bury themselves in 

 the sand. They creep about by the help of their foot in pursuit of 

 bivalves. They are found in all seas ; but the larger species and 

 greatest numbers come from warm regions, more especially from the 

 West Indian and Australian seas. 



The Purpura of the ancients was not, as is generally thought, a 

 vermilion red, but rather a very deep violet, which at a later period 

 came to have various shades of red. The secret of its preparation 

 was only known to the Phoenicians, that being most esteemed which 

 came from Tyre. Sir William Wilde has discovered on the eastern 

 shores of the Mediterranean, near the ruins of Tyre, a certain number 

 of circular excavations in the solid rock. In these excavations he 

 found a great number of broken shells of Murex trunatlus. He 

 thinks it probable that they had been bruised in great masses by 

 the Tyrian workmen, for the manufacture of the purple dye. Many 

 shells of the same species are found actually living on the same coast 

 at the present time. 



Aristotle, in his writings, dwells upon their purple dye He says 

 that this dye is taken from two flesh-eating molluscs inhabiting the 

 sea which washes the Phoenician coast. According to the description 

 given by the celebrated Greek philosopher, one of these animals had 



