2o8 TROPIC DAYS 



and since the pearl, whether produced by o3''ster, mussel, 

 pinna, or window-shell, is generally more brilliant than 

 the containing shell, that of the black pinna, with the 

 high lights of its environment concentrated, may be a 

 gem of surpassing novelty and beauty. But the habitual 

 product of this pinna is small, dull, mud-tinted or brown, 

 and of no value whatever. Another of the genera grows 

 "seed" of excellent lustre, corresponding with the azure 

 brightness of the shell. 



The chief source of orient pearls on the coast of North 

 Queensland is the gold-lip mother-of-pearl Pinctada 

 maxima, while the black lip Pinctada margaritifera 

 occasionally 3'ields fine and flawless specimens of a 

 silvery lustre. One which is still lovingly remembered 

 was of pale blue and wonderfully lighted. The com- 

 monest of the giant clams Tridacna gigas sometimes 

 betrays evidence of past internal trouble by the pres- 

 ence of a concretion of porcelain whiteness and of por- 

 cellaneous texture, but such are not to be described as 

 pearls and to be prized as rarities only. 



That some huge molluscs produced pearls before man, 

 with his faculty for admiration, came on the scene is 

 proved by their existence as fossils in chalk. Hemi- 

 spherical specimens have been found on the inner 

 surface of a shell which has no living representative — 

 viz., the Inoceramus (some of which attained a length 

 of two feet) — and spherical ones of the same prismatical 

 structure occur detached in the chalk. It were curious 

 to let the imagination run over the fact that the hosts 

 of these uncommended gems died ages before the advent 

 of man. The best of modern prizes may be punj^ in 

 comparison with those which caused distress to the 

 giant molluscs of the age when the Ichthyosaurus, 

 Plesiosaurus, and Pterodactylus were the aristocrats of 

 the animal world. Such gems have gone for ever, and 



