I 



Red Sea Shells. 17 



evident in the muscles which he exerts to open and close his shell. 

 Darwin says in his journal, writing of the clams in the lagoon of 

 Keeling Island, that a man who got his hand clinched between 

 the valves would not be able to withdraw it as long as the animal 

 lived. The shape and colour of the clam shell, which differ con- 

 siderably in the same species, are partly determined by the growth 

 of the reefs to which he anchors, and the more or less sunless 

 depths of his habitat. If he moors himself in deep still waters, he 

 becomes frilled and goffered like this ; but here is another speci- 

 men, which has manifestly known more than his companion of the 

 rubs and knocks of a sea going life. The age to which the clam 

 lives is a naatter of uncertainty, but it is supposed that some 

 monsters have outlived a century, owing tp the enormous bulk of their 

 shells, which, when prevented by the surrounding coral from grow- 

 ing outwardly, thicken internally, and become so solid as to lose 

 all trace of organic structure. One more fact about the clam, which 

 is, that he is good for food, and if well grown will feast as many 

 Indians as he weighs pounds. 



Another of the large shells I found in great abundance is the 

 Pteroceras, better known as the spider or scorpion shell. In one 

 spot I came upon a large number with horns fully grown, and 

 richly coloured lips, but the saddle bags of my camel were not the 

 most convenient kind of packing case for so eccentric a shape, and 

 I was reluctantly obliged to leave them where I found them. The 

 creature is a very interesting one, for this reason, that it exemplifies 

 in a marked manner what is perhaps the most wonderful pheno- 

 menon in the natural history of shells — namely the change which 

 takes place between the period of youth and maturity. These 

 curious projecting horns, with their sharp points and bold curves, 

 are not found at all in the baby spider, whose connection with the 

 family of strombs is at once evident, while that of its parents has 

 almost to be taken on trust. 



Look again at the Cowrie as an instance of strange metamor- 

 phosis in the opposite direction. You would mistake it for a 

 volute with its prominent spire and thin sharp lip. How comes it 

 that the old cowrie is so sleek and rounded, so different from this 

 young specimen ? It is not enough to say that the outer lip 

 gradually curls in and thickens so as to imitate the form of the 

 inner. Whence comes the substance that thickens the shell ? Why 

 are the lips serrated ? How is the spire buried ? What is the 

 cause of the deep warm colours we admire in the full grown 

 panther cowrie ? All these are interesting questions to which I 

 can do little more than hint an answer. What is a shell ? Is it, 

 as all people thought once, and many people think still, merely 

 the house of the creature that lives in it — a thing to be admired 

 c 



