526 



THE WONDERS OF GEOLOGY. Lect. V. 



certain localities : this is especially the case at Nattheim, 

 near Heidenheim, whence exquisite specimens of Litho- 

 dendron have been obtained. 



In the beds of chert in the Oolite of Tisbury in Wilts, 

 shells and corals are found in a beautifully silicified state, 

 particularly a species of Astraea {A. Tisburiensis). Large 

 silicified masses of this coral are met with, which, on being 

 cut and polished, display the intimate structure of the 

 original, and form a highly ornamental material for the 

 jewellers and lapidaries. A matchless specimen of the soft 

 parts of a Trigonia, transmuted into silex, was obtained 

 from Tisbury by the late Miss E. Benett, and is now, with 

 the greater part of the collection of that lady, in the posses- 

 sion of Mr. Wilson of Philadelphia.* 



The Crinoidea, or lily-shaped animals, are equally abun- 

 dant, and are often found in an admirable state of perfec- 

 tion. Whole slabs of many of the Lias shales are covered 

 withPentacrinites, frosted with brilliant pyrites, and lying in 

 relief on the stone, as if spread out on the sea-sand, f 



Of Echinites upwards of sixty species, and of Star-fishes 

 several genera, comprising many species, have been deter- 

 mined. Some splendid Star-fishes from the Yorkshire 

 Oolite and Lias are figured in the London Geological and 

 Palasontological Journal, pi. 17, (Asteiias arenicola), and 

 pi. 19, 20 (Ophiurce). 



28. Mollusca. — The shells, both of testaceous and con- 

 chiferous mollusks, amount to many hundred species. Of 

 the Cephalopoda, as Nautili, Ammonites, Beleranites, 

 Sepiadae, &c. several hundred species, belonging to nume- 

 rous genera, have been figured and described. J 



* Figures and a description of this extraordinary British fossil will 

 be given by Mr. Charlesworth in the Palasontological Journal, from 

 drawings by Mr. Dinkel. f See Brit. Mus. collection, 



t See Sowerby's Mineral Conchology, and the works before re- 

 ferred to. 



