220 NORTH STAFFORDSHIRE COAL FOSSILS. 



Ctenoptychius unilateralis, Barkas. (Ref., Geol. Mag., vol. 

 vii., p. 43.) Several specimens of this little-known fossil 

 have been found at Longton. It is a question yet undecided, 

 whether this is a tooth or a jaw. 



Position and locality : Deep mine, Knowles and Chalky 

 mine ironstones, Fenton and Longton. 



GENUS HELODUS, AGASSIZ. 



Helodits simplex, Agassiz. (Ref., Poiss. Foss., vol. iii., tab. 

 19, fig. 5 7.) The peculiar teeth to which Agassiz assigned 

 the title of H. simplex were found in the coal shales of 

 Silverdale. Until within a few years, teeth were all that 

 was known of this fish. About four years ago we discovered 

 in the Knowles ironstone, at Fenton, the remains of an 

 almost entire specimen of Helodus, showing the teeth, a 

 portion of the body, and a small spine. Fragments have 

 since been found exhibiting portions previously unknown. 

 We propose briefly to notice the most characteristic features 

 as shown by the fragments in our collection, reserving for 

 a future occasion a more detailed description. In none of 

 our specimens is the contour of the body shown, nor can 

 the size of the fish be accurately determined. Judging 

 from a number of specimens, the maximum length was 

 about twelve inches. Shagreen covers the whole of the 

 body ; traces of dermal tubercles can be seen scattered on 

 different portions of the fish, but in no instance is their form 

 clearly defined. At a point, probably midway between the 

 anterior and posterior extremities of the fish, there is a 

 small spine. It projects from the dorsal margin and is 

 slightly inclined backwards, apparently in its natural position. 

 In one specimen a small portion of the dorsal fin is preserved ; 

 portions of several of the other fins are also preserved. In 



