26 FISH OF THE CARBONIFEROUS PERIOD. 



Chwodus pes-ran<B (M^Coy). 



Sp. Char. Length 8 lines, narrow ; anterior lobes narrow, pro- 

 minent, rounded, arched, separated by deep concave furrows ; 

 the inner lobe about a line longer than the next outer one ; at 

 the base of the former, or about half the length of the whole 

 tooth, there projects horizontally inwards from the inner mar- 

 gin a short, wide, slightly recurved, flattened lobe, about 1 line 

 long ; posterior part of the tooth flattened ; surface finely punc- 

 tured under the lens. 

 This little species is something the size and shape of the foot 



of our common frog, whence the specific name. 



Rare, in the black shaly beds of the carboniferous limestone of 



Derbyshire. 



[Col. University of Cambridge.) 



Orodus porosus (M'Coy). 

 Sp. Char. Subcylindrical, transverse diameter (or length of base) 

 six or seven times greater than the antero-posterior ; anterior 

 and posterior margins nearly parallel, the middle being scarcely 

 wider than the ends, which are obtusely subtruncate; sides 

 slightly tumid, converging to a narrow mesial ridge ; one small 

 obtuse mesial cone not exceeding the short diameter of the 

 base in height, and forming an obtuse ridge to the base on 

 each ; on each side there are four or five smaller tubercles, the 

 smallest towards the ends, only those nearest the centre send 

 one or two small ridges down the anterior side, while the pos- 

 terior is more regularly ridged; basal margin tuberculato- 

 plicate ; surface coarsely punctured, except on the prominent 

 worn points which are smooth ; transverse diameter usually 

 about 9 lines, short diameter 1^ line. 



In one example there are three nearly equal and similar teeth 

 close behind each other ; the mesial ridge is a little nearer the 

 posterior than the anterior margin, and most so in the most an- 

 terior teeth. 



From the carboniferous limestone of Armagh. 



(Col. Capt. Jones, R.N., M.P.) 



Orodus compressus (M'Coy). 



Sp. Char. Much compressed, crown elevated into a thin edge of 

 equal height throughout, surmounted by a fine ridge and fes- 

 tooned by four or five sharp points on each side; the centre 

 has a larger point, producing a globular swelling in the middle 

 of each of the flattened sides, over which it sends a small flexu- 

 ous ridge giving out short branches on each side, while the 

 lateral points only send short simple ridges not half-way down 



