NEWTON: FOSSIL PEABL-GEOWTHS. 131 



III. Aetificial Peaels. 



That pearls could be produced by artificial means has long been 

 demonstrated by Linnaeus and others. Even from the thirteenth 

 century the Chinese adopted methods for the production of pearls in 

 the valves of the large fresh-water mussel, Barbala [Bipsas) plicata, 

 found in the rivers of their country. They inserted mother-of-pearl 

 or metal plates of small size, so fashioned as to represent images of 

 Buddha, Avhich were cleverly introduced between the mantle of the 

 animal and its shell, to the number of eleven or twelve, with their 

 heads directed in one way, mostly postero-vertically. This mechanical 

 device was accomplished during the life of the mollusc, the valves 

 being returned to the river-beds, when, after some months, a nacreous 

 secretion was found to cover the images, the valves in that condition 

 being ultimately sold as curios by the natives. Dr. J. E. Gray ^ has 

 written some interesting papers on this industry, as well as many 

 other authors. 



IV. Fossil Peaels. 



These calcareous concretions, or peaii- growths, found occasionallj' 

 adherent on the inner surface of certain fossil pelecypod valves, or 

 even in the free condition, may occur either in great numbers, when 

 they would be moderately small, or singly, when they might be of 

 considerable size. It is generally admitted that pearls are of similar 

 structure to the shells in which thej^ are found, and like them consist 

 of three layers ; in the case of adherent specimens the inner layer of 

 the shell is easily seen to form the outer layer of the pearl. 



So far as present researches have gone, it is worthy of note that 

 fossil pearls have only been observed among the genera Volsella of 

 the family Mytilidse, Inoeeranms and Perna, members of the Aviculidae, 

 and Gryphcea, one of the Ostreidse. Such relics are apparently 

 most rare, those known to the writer and which are referred 

 to in this paper being chiefly of Mesozoic age. There is no 

 reason why certain Palaeozoic Pelecypods should not exhibit similar 

 structures, yet no authentic account can at present be traced.'^ The 

 British Pliocene (Crag) deposits have yielded pearl- structures, but 

 these, in the opinion of the writer, are most probably derived and 

 had their origin in the Chalk. 



The various examples of pearl-growths found in the fossil state 

 which have come under my notice during the preparation of this 



' " On the Structure of Pearls, and on the Chinese mode of producing them of 

 a large size and regular form " : Annals of Philosophy, 1825, vol. ix, pp. 27-9. 

 "Figured Pearls of the Chinese": Ann. Mag. Nat. Hist., 1854, vol. xiii, 

 p. 238. 



2 Allusion may be made here to certain minute spherical bodies described by 

 Professor \V. J. Sollas from the AVenlock Limestone near Cardiil, which were 

 found associated with Favosites Jibrosus [ = & coxaX). From their pearly lustre 

 and slight translucency, these spheres resembled a number of small pearls, but 

 as they only showed a concentric structure mthout any trace of radiating fibres 

 they were regarded as oolitic grains formed by a deposition of carbonate of lime 

 from solution. (Quart. Journ. Geol. Soc, 1879, vol. xxxv, pp. 501, 302.) 



