44 SHELL GALLERY. 



larger than a pea, which are so highly valued. In his account of 

 the pearl-fishery of Ceylon the Rev. James Cordiner says that he 

 saw the operation of sorting the pearls performed; the produce 

 of 17,000 oysters weighed only f lb. and was contained in a 

 vessel smaller than a common soup-plate. Out of that quantity 

 there were not found two fine perfect pearls ; all of the largest were 

 slightly deformed, rugged and uneven, but of the smaller sizes 

 many were round and perfect. The chief qualities which regulate 

 the value of pearls are size, roundness, and brilliancy of lustre. Of 

 the smallest kind several may be bought for a shilling, whilst many 

 thousand pounds have been given for a single fine pearl of sur- 

 passing beauty. 



Other important pearl-fisheries besides that of Ceylon are carried 

 on in the Persian Gulf, on the west coast of Central America, and 

 especially North-west Australia, where diving-dresses are now 

 employed in collecting the shells. 



The Chinese obtain pearls artificially from a species of fresh- 

 water Mussel (Dipsas plicata). In order to do this they keep them 

 in tanks and insert between the shell and the animal either 

 small shot or small round pieces of mother-of-pearl, which soon 

 receive regular coatings of nacre and assume the look of ordinary 

 pearls. They also insert small metal images of Buddha, which 

 also soon become covered with pearl and firmly cemented to the 

 shell, the production being to the uninitiated a supernatural testi- 

 mony to the truth of Buddhism. (A shell treated in this way is 

 exhibited in one of the small cases near the entrance to the room.) 

 [Cases The Spondylidce, or Thorny Oysters, closely resemble the 



25b.1 Scallops, but the shells"°are more spiny, heavier, united by inter- 



locking teeth, and one of the valves is attached to rocks, corals, 

 &c. Many of the species are very brightly coloured ; and from the 

 fact that small quantities of water are sometimes enclosed in cavities 

 in the inner layer of the shell, they have been called " Water-Clams" 

 or "Water Spondyli." 

 "Case 25 The Scallops or Fan-shells (Pectinida) are well known for 

 B_r, J their beautiful colours, sculpture, and excellent flavour. The 



animal has a distinct foot, which is not, however, used as a loco- 

 motive organ, but employed in spinning a byssus of attachment 

 when required. The young Pectens dart through the water by 



