Fort St. Frederic. 23 



are deprefled in the middle ; but in moft 

 of them the outward furface is remarkably 

 elevated. The furrows always run longi- 

 tudinally, or from the top, diverging to the 

 margin. 



Petrefied Cornua Ammonis. Thefe are 

 likewife frequently found, but not equal 

 to the former in number : like the peEii- 

 nitce, they are found really petrefied, and in 

 impreffions ; amongft them were fome-pe- 

 trefied fnails. Some of thefe Cornua Am- 

 monis were remarkably big, and I do not 

 remember feeing their equals, for they 

 meafured above two feet in diameter. 



DIFFERENT kinds of corals could be 

 plainly feen in, and feparated from, the 

 ftone in which they lay. Some were white 

 and ramofe, or Lithophytes ; others were 

 ftarry corals, or Madrepores $ the latter were 

 rather fcarce. 



I MUST give the name of Stone-balls to 

 a kind of flones foreign to me, which are 

 found in great plenty in fome of the rock- 

 flones. They were globular, one half of 

 them projecting generally above the rock, 

 and the other remaining in it. They con- 

 fift of nearly parallel fibres, which arife from 

 the bottom as from a center, and fpread 

 over the furface of the ball and have a grey 

 colour. The outfide of the balls is fmooth, 

 B 4 but 



