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 Ovu/a, 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 
