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ON SOME FOSSIL PEAEL - GEOWTHS. 



By J, WiiFKiD Jackson, F.Gr.S. (Manchester Museum). 



Mead Uth Ai)ril, 1909. 



PLATE XIV. 



Afteh reading Mr. E. Bullen ISTewton's highly interesting article on 

 "Fossil Pearl-growths" {antea, pp. 128-39), I at once commenced 

 to hunt up specimens of fossil pearls in the collections at the 

 Manchester Museum, and am pleased to be able to add other 

 examples to Mr. Newton's list. An account of these may not be 

 without interest to readers, and may stimulate further search for 

 these objects. The following are the examples which have, so far, 

 come under my notice. For the sake of uniformity Mr. Newton's 

 excellent method of description is adopted. 



Family MYTILID^. 

 Mytiltjs edulis, Linna3us. PI. XIV, Figs. A, B. 



In the late Mr. E. D. Darbishire's large series of shells from 

 the Raised Beach of Uddevalla, there is quite a number of odd 

 valves of the above species, each containing one or more examples 

 of attached pearls. Some of the valves contain many of these 

 bodies, as will be seen by the larger example figured on PI. XIV, 

 Fig. A. Several small isolated pearls, of irregular shapes and varying 

 in size, are also included in the same collection. 



Geological age. — Post-Pliocene (Raised Beach). 



Locality. — Uddevalla, Sweden. 



Collection. — Manchester Museum (R. D. Darbishire Coll.) [L. 3120]. 



Family AVICULID^. 

 Inocehamds (?). PL XIV, Fig. C. 



Amongst a large collection of Cambridge Greensand fossils presented 

 by the Rev. A. Dixon in 1901, I recently came across a rather fine 

 example of a pearl. Its greatest diameter is 9 mm., and various 

 growth layers can be seen in places where the outer crust has been 

 fractured. The colour of the pearl is a dirty steel-grey. Like the 

 Crag examples, no doubt this specimen was of derivative origin. 



Geological age. — Cretaceous (Albian). Found in the so-called 

 Cambridge Greensand. 



Locality. — Cambridge. 



Collection. — Manchester Museum (Rev. A. Dixon Coll.) [L. 8702]. 



Inoceramus. pi. XIV, Fig. D. 



The Manchester Museum possesses three examples of pearls from 

 the Crag deposits of Suffolk, presented by Mr. R. Cairns. In general 

 characters they agree with the British Museum specimens referred 

 to in Mr. Newton's paper (see pp. 136, 137). One, however, is still 

 attached to a small portion of the shell. 



