NORTH STAFFORDSHIRE COAL FOSSILS. 231 



Position and locality : Deep mine, Knowles, and Chalky 

 mine ironstones, Fenton and Longton. 



GENUS RHIZODOPSIS, HUXLEY. 



Rhizodopsis sauroides, Huxley. Holoptychius sauroides, 

 Agassiz. (Ref., Quar. Jour. Geol. Soc., vol. xxii., p. 59 60.) 

 This species is not rare, and is widely distributed. Many 

 fine specimens have been found in the Knowles ironstone. 

 The length of the fish ranges from three inches to eighteen 

 inches or more. The body tapers posteriorly. The greatest 

 depth is immediately behind the pectoral arch. The body 

 of the fish is covered with orbicular-shaped scales, which 

 cross the body obliquely. The upper surface is ornamented 

 with fine, concentric radiating stria?. The head is much 

 flattened and the gape is wide. The maxilla is filled with 

 fine, conical teeth. The mandible is straight, broad at the 

 symphysis, and contains teeth of two sizes ; the largest, four 

 in number, long and sharp, slightly incurved. The outer 

 margin is set with small, strong, conical teeth. There are 

 two jugular plates, but no lateral plates. These are orna- 

 mented like the operculars with fine, parallel ridges. The 

 pectoral fins are well shown in many of our specimens. In 

 a specimen ten inches in length, the pectoral fins measure 

 two and a half inches in length, and one and a half inch 

 in breadth. They are acutely lobate, with rounded margins. 

 The central stem in each fin is covered with scales. The 

 most complete specimens occur in ironstone nodules. In 

 these, the osseous rings composing the vertebral column are 

 frequently preserved in situ. Our collection contains several 

 small specimens of about four inches in length. The scales 

 are much thinner than in those of the larger individuals, 

 At present, it is not clear whether or not they are 

 specifically distinct from the larger specimens. 



