306 



THE WONDERS OF GEOLOGY. 



Lect. IV. 



Figs. 4, o, 6, represent the three best defined specimens 

 highly magnified.* 



Lign. 54.— Xanthidia in Flint, 



{By Reginald Neville Mantell.) 

 Fig. 1. A thin, transparent, chip of flint: natural size. 



2. The same magnified, viewed by transmitted light. 



3. More highly magnified. 



A. Xanthidium ramosum ; one of the animalculites seen m the previous figure*, 

 magnified 300 diameters. 



5. Xanthidium Reginaldi; from the same group : a very rare species. 



6. Another variety of Xanthidium ramosum. 



9. Middle and lower group of the chalk for- 

 mation.— Beneath the Chalk with flints, is a series of 

 strata of equal thickness, termed the Lower Chalk, in 

 which no flints are met with in England, except in a few 

 localities ; in some places on the Continent, however, nodules 



* The Xanthidia which occur in the English chalk flints, were 

 first noticed and figured by the Rev. J. B. Reade, in the Annals 

 of Nat. Hist. 1838; they have since been made the subject of aD 

 elegant memoir, published in the Transactions of the Microscopical 

 Society of London, vol. i. p. 77, by H. Hopley White, Esq. of Clapham. 

 A specimen from chalk, by Mr. Deane, is figured iu Plnlos. Trans. 

 1846, PI XXI. fig. 1. 



