ANIMALS. 221 



Sub-kingdom VERTEBRATA, Cuvier. 



Of the present division of Animated Nature, Fishes and Reptiles are the only- 

 groups requiring notice in this Monograph ; since no remains of Birds and Mammals 

 have yet been found in deposits belonging to the Permian period. 



Class Pisces, Linnaeus. 



According to the system of Agassiz, this class consists of four orders, namely, 

 Placoidei, Goniolepidoti, Ctenoidei, and Cycloidei. Of these, the first two alone require 

 consideration in this Monograph, as all the Ichthyolites of the Permian age are 

 referable to them. 



Order Placoidei, Agassiz. 

 Plagiostomi, Cuvier. 



Family CESTRACiONTiDiE, Agassiz. 



Genus Gyracanthus, Agassiz. 



Gyracanthus formosus, Agassiz. 



Petrified wood. Tire. History of Rutherglen, pp. 303, 304, pi. xii, fig. 6. 



A EEMAKKABLE FOSSIL,^ J. de C. Sowerhy. Zoological Journal, vol. ii, pp. 252, 253, 



pi. viii, fig. 9. 

 GYRACANTHUS FORMOSUS, Agassis. Poissons Fossiles, vol. iii, p. 17, pi. v, figs. 4-8. 



— — „ King, Catalogue, p. 14, 1848. 



— Howse, Trans. T. N. F. C, vol. i, p. 237, 1848. 



"The Newcastle Museum possesses a fragment of a fossil, which I am happy in 

 making out to be an Ichthyodorulite or dorsal spine of an extinct family of sharks. It 

 is the impression of the inferior part of the anterior face, showing the entire length of 

 the root and a small portion of the obliquely ridged part : the root is longitudinally 

 striated, and the obliquely ridged part tapers off to a point on the mesial line of the 

 anterior face : the point is an inch and a quarter from the termination of the root. I 

 feel persuaded that it is the Gyracanthus formosus.'''''^ 



1 Mr, Sowerby adds, " most probably belonging to a Fish." 



2 King, Catalogue, p. 14. 



