NORTH STAFFORDSHIRE COAL FOSSILS. 219 



Position and locality : Not rare in the Rag mine, Fenton, 

 and Brown mine ironstone, Silverdale ; more rare in the 

 Knowles, Chalky, and Deep mine ironstones, Fenton and 

 Longton. 



Ctenoptychms denticulatus, Agassiz. (Ref., Poiss. Foss., 

 vol. in., tab. 19, fig. 5 7.) This species is not uncommon 

 in the Deep mine ironstone at Longton. The crown of the 

 tooth is plate-like, swollen on the exterior surface, the 

 internal concave. The margin of the crown is denticulated 

 with parallel denticles nearly equal in size, and rounded. 

 We have several specimens in which the tooth-plate is much 

 elongated, and has upwards of twenty-six denticles. The 

 base of the tooth is nearly double the height of the crown : 

 it contracts gently below the denticulated margin ; the 

 lower portion is produced into fang-like processes, from 

 three to seven in number, according to the breadth of the 

 tooth. 



Position and locality : Deep mine and Rag mine iron- 

 stones, Fenton and Longton. 



Ctenoptychms pectmatus, Agassiz. (Ref., Poiss. Foss., vol. 

 iii., tab. 19, fig. 2 4). This tooth is moderately common 

 in the Rag mine ironstone. The crown of the tooth is 

 arched transversely, and the upper margin denticulated. 

 The internal surface of the crown is concave, the external 

 surface convex ; a deep constriction separates the crown 

 from the base. The base is contracted below the denticulated 

 margin, and the lower portion, as in the preceding species, 

 is produced in four or more fang-like processes. 



Position and locality : Deep mine and Rag mine iron- 

 stones, Fenton and Longton. 



