142 Rev. A. Sedgwick arid Mr. Murchison on Deposits contained between 



each other considerably in composition. One of them gave the following- 

 result. 



Silex G8.1 



Alumine 7.2 



Protoxyd of iron 10.5 



Carbonate of lime and magnesia . 14.2 



100.0 

 The jiroportion of magnesia is very small. The blue matter of the fish is 

 phosphate of iron, and the whole stone contains phosphoric acid in the pro- 

 portion of ^ per cent, and a little carbonaceous and bituminous matter. The 

 iron being a protoxyd, the fresh fracture is black ; but, by absorbing oxygen, 

 it becomes yellow, and the phosphate passes into a per-phosphate, becoming 

 blue. Thus the fish are visibly marked with blue streaks on a yellow ground. 

 With respect to the systematic arrangement of these fossil fish. Baron 

 Cuvier has communicated the following valuable description of those from 

 Banniskirk, which were sent to him (1827) for his opinion*. 



''To describe the characters of the fossil fish on which Mr. Murchison has 

 requested my opinion, I have endeavoured to trace an outline of an entire one, 

 by reassembling the parts as seen in the different specimens. The result is 

 the accompanying sketch f, which exhibits, as an essential character, a pointed 

 tail, all the rays of which are on the lower side. This character is found in 

 the fish of the copper schists of Mansfeldt and Eisleben. In animated nature, 

 I am acquainted with no fish having this distinction, except the bony pike 

 {Esox osseiis'l, Linn.), and in a slighter degree the sturgeon; but as these 

 fossil fish have strong scales, I should rather refer them to the bony pike. 

 They are not, however, of the same genus, since they have not an elongated 

 snout. The fish of Mansfeldt and Eisleben are, therefore, very nearly of the 

 same genus (genre), as those of Banniskirk, except that the latter have a 

 double dorsal fin, whilst those of Thuringia have only a single dorsal, which 

 is placed further forward. The pectoral and ventral fins {nageoirs pairs) 

 are alone wanting for the complete determination of these individuals ; they 

 exhibit some remains of pectoral fins, but I have not yet been able to dis- 

 cover more than one vestige of a ventral fin. I am of opinion, however, that 

 the ventral fins are placed so far behind the pectoral fins, that, consequently, 

 this genus is of the order Malacopterygii abdominales, and is, therefore, ana- 

 logous to the bony pike." 



* These specimens consisted only of a small number of the whole series afterwards examined 

 by Messrs. Valenciennes and Pentland, 



t Plate XV. fig. 4. % Lepisosieus, Lacep. 



