226 NORTH STAFFORDSHIRE COAL FOSSILS. 



vol. iii., tab. 45, fig. 4 6.) A few specimens of this for- 

 midable fin-spine have been found in various parts of the 

 coalfield. The largest of these is about six inches in length, 

 rather flat at the base, but rounder towards the point. For 

 about half its length the lateral margins are armed with 

 tine spine-like teeth, pointed downwards. Along the basal 

 portion of the spine there is a round, deep groove. 



Position and locality : Deep mine, Rag mine, and Chalky 

 mine ironstones, Fenton and Longton ; Brown mine, Silver- 

 dale and Kidsgrove ; Gubbin ironstone, Shelton. 



Plearacantkus n. sp. Our collection contains several small 

 spines which are specifically distinct from P. lasvissimus. 

 The spine is about two-and-a-half inches in length, and 

 nearly circular in section. The lateral margins are armed 

 with seven or eight spines crowded together near the summit. 



Position and locality : Deep mine and Chalky mine 

 ironstones, Longton. 



ORDER GANOIDEI. 

 FAMILY SAUROIDEI, AGASSIZ. 



GENUS ACROLEPIS, AGASSIZ. (Ref., Poiss Foss., vol. ii., 



p. 79.) 



Detached scales, which we refer to this rare genus, 

 have occurred in several of the ironstones. The scales are 

 thick and rhomboidal or lozenge-shaped. The upper 

 portion is marked with thick, rounded, anastomosing ridges 

 in the direction of the longer axis. 



