438 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. V. 



Ooprolites of Macropoma. (No. 13.) There is a large num- 

 ber of coprolites in this Case, which in all probability are 

 referable to these fishes. They show that the spiral convolu- 

 tions were fewer in the intestines of the Macropoma than in 

 the Sharks. 1 



Lophiostomus Dixoni. The chalk ichthyolite thus named 

 (by Sir Philip Egerton) is from a quarry near Alfriston, in 

 Sussex, and was collected by Captain Beckford, R.N. of Ryde, 

 in whose choice cabinet of fossils I detected it as an unknown 

 ganoid fish, and induced the liberal owner to add it to the 

 National Collection. It will be figured and described in the 

 " Memoirs of the Museum of Practical Geology." It is allied 

 to the Macropoma, but differs in many essential characters : 

 the large mouth garnished with numerous very small, slender, 

 conical, fluted teeth, its granulated cranial plates, the form 

 and structure of the lower jaw, the branchial plates, and the 

 scales, which Professor Williamson informs me are altogether 

 peculiar, render it a valuable addition to the Ichthyolites of 

 the British Museum. The specific name was proposed by me, 

 to commemorate the late F. Dixon, Esq. of Worthing. 



SCLERODERMS. This family of ganoids, to which the Dio- 

 dons and Ostracions belong, besides certain peculiar modifica- 

 tions of the jaws, is distinguished by the dermal integuments, 

 w r hich consist of polygonal or rhomboidal plates, spread over 

 the body like a tesselated cuirass ; the skeleton is fibrous ; 

 the recent types are exclusively the inhabitants of the seas of 

 hot climates. 



Dercetis elongatus. 2 Wall-case 0. (No. 15, 16, Middle 

 shelves.) This is a very remarkable fossil fish from the 

 chalk, near Lewes, which I discovered in 1818. The speci- 

 mens commonly met with consist of fragments of the long 

 subcylindrical body, covered with small scales, from a few- 

 inches to two feet in length, without any traces of the dermal 

 scutcheons, fins, tail, or head: as in many examples in this 

 Case, all of which are from my collection. The Dercetis had 

 on each side of the body three rows of dermal scutcheons, 

 like those of the Sturgeons ; the intervals between them were 



1 See " Medals of Creation," p. 650. 



2 " Murcena ? Levvesiensis." " Fossils of the South Downs/' tab. xxxiv. 

 fig. 10, 11. See " Medals of Creation," p. 658. 



