128 



FOSSIL PEARL- GROWTHS. 



By R. BuLLEN Newton, F.G.S. 



Bead Sth May, 1908. 



PLATES IV AND V. 



I, Inteodtjction. 



Although much has been written on the history of modern pearls, 

 very few records appear to exist calling attention to the occurrence of 

 such bodies in the fossil state. John Woodward, in 1723 (" An Essay 

 towards a Natural History of the Earth," 3rd ed., p. 24), briefly referred 

 to the fact that fossil shells, as well as i-ecent, had " pearls and the 

 like still actually growing upon them." In 1836 Goldfuss^ figured a 

 natural internal cast of an example of Inoceranius Cripsii {non Mantell) 

 from the German Cretaceous deposits, with numerous pittings which 

 were doubtless the result of pearl)'- protuberances developed on the 

 inner surface of the valve. 



The late Professor John Morris * published some interesting notes in 

 1851, with illustrations, which are of sufficient interest to reproduce : 

 " Pearl-lihe bodies. — Most persons are aware that some forms of the 

 conchiferous mollusks are subject to certain abnormal secretions, 

 assuming a more or less regular form, and composed of fibro -calcareous 

 matter generally arranged in a concentric manner ; sometimes it is 

 solidly attached to the inner layer of the shell, of which it forms 

 a portion ; at others it is found perfectly free in the fleshy substance 

 of the mollusk itself, of a symmetrical shape, as in the perfect pearl. 

 Evidence of phenomena resulting from similar conditions has been 

 detected in certain fossil genera, but few, if any, instances have been 

 recorded. The collection of Mr. "Wetherell contains many illustrative 

 specimens; in one, a Gryphcea [_dilatata] from the Drift of Muswell 

 Hill, and probably coming from the Oxford Clay [really Kimeridge], 

 is an irregular elongated body, free at both ends, but attached by 

 a considerable portion of its surface, the external lamina being 

 continuous with the shell; the outer layers do not, however, show 

 the regular fibrous arrangement of a perlaceous body, but this may 

 have been changed by subsequent mineralization. In another 

 specimen the pearly body is attached to the interior of an Inoceramiis, 

 and shows the concentric arrangement of the fibrous substance, and 

 which is better exhibited in the specimen showing a complete section 

 of one of considerable size, quite unattached to any shell, from the 

 Chalk of Kent." The material which formed the subject of Professor 

 Morris' statements is now in the collection of the British Museum. 



Ten years later (1861) Professor H. G. Seeley^ described Perna 

 ohlonga, the valves of which occurred as natural casts in the phosphatic 



1 Petrefacta Germaniise, 1836, vol. ii, p. 116, pi. cxii, fig. ^d. 



2 Ann. Mag. Nat. Hist., 1851, vol. viii, p. 85, pi. iv, figs. 12, 13, 14, 16. 



3 Ann. Mag. Nat. Hist., 1861, vol. vii, p. 121, pi. vi, fig. 6. 



