from the. Shales of the Northumherland Coal-field. 347 



approaches in form to the mahar of the Alligator, and reminds 

 one somewhat of the bone in Asterolepis considered by Agassiz 

 to be a premaxillary* ; but in our specimen the articular por- 

 tion is wanting. The other bone is apparently the posterior 

 part of a mandibular ramus with a wide articular process at 

 the hindermost part, not perfect though very distinctly dis- 

 played. The former of these bones is quite four and a half 

 inches long, and upwards of one inch wide at the broadest 

 part ; it is thin in front, thickens backwards, and bends rather 

 abruptly down at the posterior extremity, which is broken. 

 Along the under margin there is a wide, flat, thin, squamous 

 process, probably for the articulation of the maxilla ; the op- 

 posite margin is not perfect ; but in a smaller specimen of the 

 same bone a similar flat articular process extends from the 

 upper margin also. 



The bone which we suppose to be the posterior portion of a 

 mandibular ramus is nearly five inches in length and one and 

 a half inch wide, including the lateral squamous expansions ; 

 it is thin, flat, and rounded in front ; behind it is much thicker; 

 and though the posterior extremity is wanting, the greater 

 portion of the articular process is present ; it has a wide 

 oblique glenoidal surface. The lateral squamous expansions 

 will undoubtedly articulate with the dentigerous bone. 



Other interesting bones have also occurred, some of which 

 can be identified as jugulars. One distorted and folded mass 

 comprises two large jugulars, apparently the pair of principal 

 plates. A considerable portion of one of them is well dis- 

 played, exhibiting in very good condition the surface-orna- 

 ment. Were this plate unfolded, it would be about seven 

 inches long and two and a half inches wide. Three or four 

 inches of what seems to be the posterior portion lies flat upon 

 the matrix, and shows the contour quite perfectly. The plate 

 is apparently equally thin throughout ; and the outer margin 

 seems, judging from the portion that is displayed, to be pretty 

 regularly arched, and the posterior margin to be rounded and 

 sloped a little forwards towards the inner border. 



Another bone, probably also a jugular, is worthy of notice. 

 This appears to be an anterior plate ; nearly one-half of it can 

 be made out : it is symmetrical, having a stout angular midrib 

 with two lateral wing-like expansions. When entire, it would 

 be four and a half inches wide and one inch and three-quarters 

 long. It is impossible to overlook the resemblance of this 

 bone to the jugular plate of Asterolejjis ; and, like it, this pro- 

 bably fitted into the top of the arch formed by the junction of 



* Poissons Fossiles du Vieux Gres Rouge, troisieme livraison, p. 95, 

 tab. 32. figs. 18, 19. 



25* 



