﻿1 IS ICHTHYODORULTJ B8. 



II. Slender elongated spines, bilaterally symmetrical, with the 

 internal cavity only open at the extremity of the base, and 

 little or no smooth inserted portion. 



Genus GNATHACANTHUS, Davis. 

 [Trans. Boy. Dublin Soc. [2] vol. i. 1883, p. 363.] 



Spine laterally compressed, with one margin acute, the other flat- 

 tened ; sides ornamented with longitudinal ridges, smooth or tuber- 

 culated ; acute margin with a single series of large denticles, flattened 

 margin with a double series of smaller denticles. 



The base of the spine is unknown, and Gnathacanthus is thus only 

 provisionally placed in this group of Ichthyodorulites. 



Gnathacanthus triangularis, Davis. 



1883. Gnathacanthus triangularis, J. W. Davis, torn. cit. p. 363, pi. xlviii. 

 fig. 11. 



Type. British Museum. 



The type species. 



Form. Sf Log. Lower Carboniferous Limestone : Armagh. 



P. 2891. Type specimen. Enniskillen Coll. 



Gnathacanthus striatus, Davis. 



1883. Gnathacanthus striatus, J. W. Davis, torn. cit. p. 364, pi. xlviii. 

 fig. 12. 



Type. British Museum. 



Form. $ Log. Lower Carboniferous Limestone : Armagh. 



P. 2892. Type specimen. Enniskillen Coll. 



P. 2892 a. Fragment. Enniskillen Coll. 



Genus APATEACANTHUS, nov. 



Spine elongated, slender, very gradually tapering, extremely com- 

 pressed laterally ; sides ornamented with irregular series of tuber- 

 culations ; posterior border with one (? or two) close series of acute, 

 hook-shaped, downwardly-pointing denticles. 



