from the Shales of the Northumherland Coal-field. 367 



quarters of an inch wide, and, including the pedicle to which 

 it is attached, it is one inch and three-quarters long; the 

 under lobe is not much produced, and the upper is rather 

 obtuse; no rays are perceptible. The scales are well pre- 

 served, and are in an undisturbed state. Some of them are 

 brilliantly glossy, and have towards the posterior angle a boss- 

 like swelling ; others are dull and minutely granular. Which 

 is the true natural surface it is difficult to say, though it seems 

 probable that the latter is. Be this as it may, both kinds of 

 scales are found scattered in the vicinity of the head and 

 spine. 



Acanthodopsts Egertoni^ n. sp. 



A crushed head with the pectoral spines attached, a de- 

 tached jaw or two, a few separate spines, and some scattered 

 scales are all the remains that have occurred of the large 

 species alluded to. The head, which could not have been less 

 than two and one-quarter inches long, has one of the man- 

 dibular rami well displayed, with the teeth attached ; but they 

 are, unfortunately, in a very imperfect state. The ramus is 

 very similar in character to that of A. Wardi- but the den- 

 tigerous bone does not appear to be striated ; the styliform 

 process is not much arcuated at the proximal extremity, and 

 tapers gradually to the anterior point. The teeth are arranged 

 in the same manner as in the smaller species — that is, with the 

 larger in the centre and smaller at the extremities of the jaw ; 

 with the aid of a detached mandible we are able to ascertain 

 that there are seven or eight in each ramus ; they are not 

 nearly so wide at the base as in the previous species, and they 

 are more regularly and finely striated. Some of the bones of 

 the head are finely and regularly tuberculated ; these are pro- 

 bably the orbital plates. The similar plates of the other 

 species appear to be irregularly granular. 



The spines attached to the head are upwards of two and a 

 half inches long, though they are not entire ; but the largest 

 detached specimen in our possession is quite an inch longer, 

 though in it, too, the point is broken. This must have been 

 longer than the largest mentioned by Sir P. Egerton ; it is 

 upwards of one-quarter of an inch broad, and is flat and 

 curved like the others, resembling the blade of a scimitar; 

 towards the base the inner margin is thickened and angulated, 

 and a depressed line or groove extends from end to end a little 

 within the anterior or arched margin ; a few fine longitudinal 

 lines are seen near to and almost parallel with the opposite 

 margin ; the point appears to be rounded, but is not quite per- 

 fect in any of our specimens. 



The scales which are found associated with the head and 



