THE COLOURS OF COWRIES 359 



the whole of the lower surface. There are, however, other 

 cowries differing from these by the development of rugosities 

 on the back, and the extension of the teeth of the mouth 

 right across the lower surface. Both these features may 

 safely be regarded as indications of greater specialisation 

 than exists among any of the typical cowries. One type 

 is represented by the pustuled cowry, in which the orna- 

 mentation on the upper surface takes the form of small 

 spherical pustules, frequently of a bright red colour, when 

 they recall a fragment of wood overgrown with funguses. 

 In the second, a still more advanced modification, the 

 ornamentation of the back assumes the form of transverse 

 ridges, which in some species are comparatively wide apart, 

 and separated by a considerable interval in the middle 

 line, whereas in others, like the little European cowry 

 Trivia europaea), they are so closely approximated, and so 

 nearly meet in the middle line, as to give the idea of a 

 small and neatly parted head of hair. 



Even these by no means exhaust the modifications which 

 the cowry type is capable of assuming, as witness the pure 

 white '' poached egg " and the " weaver's shuttle," both 

 members of the genus Ovula, the latter remarkable for the 

 elongation of the two extremities of the mouth into tube- 

 like processes. Both these, as well as certain other allied 

 types, depart from the ordinary cowry type by their white 

 or pinkish colour, and are therefore evidently specialised 

 modifications. In the case of the weaver's shuttle the colour 

 is probably produced to harmonise with the sea-fans, upon 

 which these molluscs are 'parasitic ; but further information 

 in regard to the reason for the absence of colour is requisite 

 in the case of the other kinds. 



One result of this brief dissertation on cowries is to show 

 how short-sighted was the idea prevalent some years ago that 



