378 LOWER FORMS OF MARINE LIFE 



(Micrex tenuispina). Of a stouter type is the Mediterranean M. brandarius, one 

 of the species yielding the famous Tyrian purple. 



A closely related family is formed by the well-known cowries (Cyprceidce), 

 most of which are characterised by the highly polished enamel of their shells. 

 Cowries are recognisable at a glance by the straight and narrow mouth of the 

 shell bearing a number of parallel vertical ' teeth ' on the sides and terminating 

 at each end in a deep channel, the lip being turned in, and the spire in adult 

 specimens almost or completely concealed or overlaid with enamel. Among the 

 larger tropical species is the Argus cowry (Cyprcea argus) of the Eastern seas, 

 which grows to about four inches in length, and takes its name from the rich 

 brown rings on a yellowish ground. In the dark and handsome Mauritius cowry 

 (C mauritiana), ranging from the island from which it takes its name to 

 Christmas and the Cocos-Keeling Islands, the shell is of much broader type, and 

 has the middle of the chocolate-brown upper surface marked with closely 

 approximated paler spots, which are in some cases distinct, but in others tend to 

 run together. Of a similar type, both as regards shape and colouring, is the 

 snake's-head cowry (C. capwt-serpentis), in which the spots are relatively smaller 

 and more thickly crowded. Another beautiful type is presented by the large and 

 handsome tiger cowry (0. tigris) of the Indian Ocean. The shell is marked by a 

 nearly straight reddish brown longitudinal line, indicating the margins of the 

 fleshy mantle by which it is covered when the soft-parts of the animal are 

 protruded, on either side of which are a number of large indistinct blackish brown 

 spots and blotches on a bluish white ground. Of somewhat similar shape and size 

 is the handsome orange cowry (C. aurantiaca) of the tropical Pacific, so called from 

 its uniformly rich orange shell, which formerly commanded a very high price. 

 An altogether different type occurs in the well-known money cowry (C. m,oneta), 

 of the Indo-Pacific, in which the shell is an inch or less in length, with an 

 irregular surface and a yellowish colour. In common with the somewhat longer 

 and more regularly formed shells of the ring cowry (C. anniulws), which are also 

 cream-coloured with an orange ring on the upper surface, money cowries were 

 formerly used extensively as a medium of exchange in India and the islands of 

 the Pacific, as well on the west coast of Africa, to which they were imported in 

 large quantities. One small species, 0. (Trivia) europcea, in which the vaulted 

 shell is marked with fine parallel transverse ridges and grooves, and is of a fleshy 

 pink colour, is not uncommon on the coasts of Britain and other European 

 countries, but bears no comparison in "point of beauty to its tropical relatives. 

 The shuttle-shell (Radulus volvula), belonging to the allied family Ovulidce, is 

 remarkable for the production of the two ends of the mouth into long, beak-like 

 channelled processes. These and other species of the same genus live on the 

 so-called bark-corals of the family Gorgoniidce, some of the smaller kinds 

 harmonising in colouring with the particular gorgonias on which they take up 

 their quarters. 



To a different group belongs the curious Magillus antiquus, of the Indian 

 Ocean, which in the young state is free and not unlike a periwinkle in shape, but 

 eventually takes up its home in a coral-reef, where it forms as an extension of the 

 mouth of its shell a long irregular, white calcareous tube which continues to grow 



