248 GEOLOGY OF THE ISLE OF WIGHT. 



evidence as to the origin of these problematical 

 objects is still desirable. 



Molluskite. — The soft bodies of the testaceous 

 mollusca often occur in a fossil state, changed into 

 a brown carbonaceous substance, which I have 

 proposed to distinguish by the term molluskite.* 

 When empty shells are found enclosed in rocks, 

 the mineral matter generally fills up the cavity and 

 forms a cast of the interior; but if the animal 

 occupied the shell at the time it was imbedded, 

 the soft parts appear to have become changed 

 into a brown or black substance, which in some 

 instances retains the form of the original, but 

 in general occurs as an amorphous mass, con- 

 taining a large proportion of animal carbon. In 

 the greyish green sands of the firestone of Kent 

 and Sussex this substance often occurs, and it is 

 equally abundant in some of the sandstones of 

 the Uridercliff. The brown spots dispersed through 

 the stone forming the mouldings and mullions of the 

 new church at Ventnor, are composed of molluskite. 

 In recently extracted stone at Ventnor, I have ob- 

 served shells of trigoniae, rostellaria?, and cucullea, 

 filled with this carbonaceous matter. The shelly 

 limestones of the Wealden, called Sussex and Pur- 

 beci marbles, are mottled with black molluskite, 



* Medals of Creation, vol. i. p. 431. 



