270 



KNOWLEDGE 



[December 1, 1898. 



historic, poetic, and romantic associations, in traditions 

 and legends, in folk-lore, customs, and dialect, that, turn 

 whichever way you will, something new and interesting is 

 invariably to be found. 



THE COLOURS OF COWRIES. 



By E. Lydekker. 



AMONG all the treasures of the shell-cabinet few are 

 more generally attractive than the cowries, or 

 kauris (Cypraa), which form the type of a family by 

 themselves. Kivalling the olives in the brilliancy 

 of their polished enamel, they exceed those shells 

 in the beauty and diversity of their coloration, while their 

 form in the adult state is so peculiar as to attract the 

 attention of even the most unobservant. Possibly, the 

 very fact that many of them, like the tiger and Surinam - 

 toad cowry, are so common as to be employed as decorative 

 objects for our chimney pieces, has, to a certain extent, 

 detracted in popular estimation from their many striking 

 peculiarities. But even if this be so, a moment's com- 

 parison with any other shell will at once show how dilferent 

 they really are. And if rarity be an additional attraction, 

 some, among the couple of hundred or so of living species, 

 are worthy of attention even from this not very elevated 

 standpoint. Take, for instance, the prince cowry (C. 

 princeps) and the spotted cowry (C. iiuttata), examples of 

 which have sold respectively for forty and forty-two pounds 

 each ; while the beautiful orange cowry, used as a head 

 ornament by the chiefs of the Friendly Islands, formerly 

 fetcheil about twenty pounds, although good specimens can 

 now be bought at from three pounds to five pounds. Other 

 species claim attention on account of their commercial 

 uses, the ring cowry being employed by the islanders of 

 Eastern Asia for personal adornment, for weighting their 

 fishing nets, and as a means of exchange ; while in the 

 latter respect the well-known money cowry has a still more 

 extensive use over a large part of Asia. 



But it is from the pecuharities of their structure and 

 coloration that these beautiful shells must claim our atten- 

 tion in the present article. Taking any common species, 

 such as the one shown in the centre of Fiu;. 1, it will be 

 seen that the upper surface of the shell approaches more 

 or less to an egg-shape, with a notch at each extremity 

 forming the terminations of the mouth below. Somewhat 

 to the right of the middle line in most species runs a 

 straight or slightly sinuous streak over which the pattern of 

 the rest of the upper surface does not extend, this line 

 marking in the living animal the Umits of the right and 

 left lobes of the so-called mantle, which during activity 

 extend upwards from the foot on which the creature crawls 

 to envelope the rest of the shell. Compared with an olive, 

 in which it is relatively small, the shell of an adult cowry 

 differs by the almost or complete absence of a distinct 

 spire ; while on the under surface the narrow mouth of the 

 shell (not, be it understood, of the animal) is remarkable 

 for the series of vertical ridges, or " teeth," with which its 

 edges are armed. 



Now, since almost all other univalve shells related, even 

 remotely, to the cowries, have a more or less elongated 

 spire at the hinder or upper end, the enquirer naturally 

 seeks to tind out the reason for the disappearance of this 

 part in the members of the present group. In a lully adult 

 specimen of the common black-spotted tiger cowry no trace 

 at all of the spire can be detected, but in the equally common 

 Surinam-toad cowry a more or less distinct remnant, partly 

 buried in the abundant cement, is observable even in the 

 adult. In Scott's cowry, of which an adult specimen is 



shown in the centre of Fig. 2, the spire is much more 

 pronounced ; and in a half-grown specimen of the same 

 species (left side of the same figure) it is so elongated as 

 to project considerably beyond the hinder extremity of the 

 shell. The same specimen also shows that in immature 

 examples of this species the hinder extremity of the right 

 margin of the shell is expanded into a wing-like extension, 

 recalling the wing-shells, or Sti-omhida. In both the adult 

 and the young of Scott's cowry the coloration is very 

 similar ; but in the young shell shown on the right of 

 Fig.*2, which belongs to the Surinam-toad cowry, there is 

 a difference both in form and in colour from the adult. In 

 form the shell has a distinct spire, and a thin outer lip ; and 

 if a still younger example were selected it would be found 

 that these characters were still more exaggerated, the mouth 

 being entirely devoid of teeth, and the outer lip quite thin 

 and sharp. Moreover, whereas the upper surface of the 

 adult shell has a broad dark brown margin, and the 

 central area spotted with light brown on a ground 

 of dark brown, the young exhibits dark and light transverse 

 bands, with a certain amount of mottlmg. 



Young cowries, then, are much more like ordinary sheila 

 than are the adult, and clearly indicate that the latter 

 belong to a highly modified or specialized type. The 

 alteration is produced by the expansion of the mantle- 

 lobes of the adult, which deposit a shining enamel over 

 the entire shell, eventually concealing, more or less com- 

 pletely, the spire, and thus totally modifying the original 

 form. A young cowry is, indeed, much more like an oUve 

 or a melon-shell : but, as a matter of fact, neither of the 

 two latter are the nearest relatives of the Cijpraida, among 

 which are the Stromhida, or wing-shells. And in this 

 connection the near resemblance of the young of Scott's 

 cowry (Fig. 2, a) to a wing-shell is decidedly worthy of 

 note, as suggestive of a direct afiinity between the wing- 

 shells and the cowries. 



Turning now to the interesting problem of coloration, 

 the first feature that must attract the attentive observer 

 is that the striking pattern developed on the shells of most 

 cowries is seldom seen by the animals themselves, for the 

 reason that by the time the creature is fuUy protruded 

 from its shell, the upper surface of the latter is more or 

 less completely concealed by the fleshy lobes of the mantle. 

 Accordingly, it would seem to be apparent that the 

 colouring of these moUuscs is developed for the purpose 

 of protection, and not for the admiration of the different 

 individuals or sexes of the same species. It might, indeed, 

 be urged that as the lobes of the mantle are coloured 

 similarly to the shell, or even more intensely, the colours 

 are visible to the animals, and are therefore designed for 

 mutual admiration. But had this been the object, it would 

 surely have sufficed to restrict the coloration to the outer 

 surface of the mantle-lobes, and not to have extended it 

 on to their inner surfaces, from which it is deposited on 

 the shell. As regards the utiUty of the cowry type of 

 coloration for protective purposes, I have never enjoyed 

 the opportunity of seeing the living moUuscs in their 

 native haunts, nor have I come across any description 

 from those who have. Cowries, which are mostly tropical 

 or sub-tropical animals, are, however, described as living 

 in shallow water not far from the shore, and feeding on 

 zoophytes ; and, so far as one can judge, their colours 

 ought to harmonize well with the hues of the denizens of 

 a coral-bank, or a mass of sea-anemones, many of which 

 are more or less similarly spotted. If this explanation 

 prove to be the true one, we can readily see why both the 

 shells and the hard parts of cowries partake of the same 

 striking types of coloration. 



Turning now to the consideration of the various types 



