416 MESSRS. HANCOCK AND ATTHEY 



C(ELACANTHUS LEPTURUS, Agassiz. 



We have long had in our possession certain mandibuliform 

 bones from the Newsham shale, evidently piscine, though we 

 could not make out to what species or even to what genus they 

 belonged ; and it was not till some short time ago, when we for- 

 tunately obtained a crushed head of Ccelacantluis, that the enigma 

 was solved. This specimen exhibits our supposed mandible in 

 connexion with the rather strangely formed bone figured and 

 described in the " Memoirs of the Geological Survey," Decade 

 12, by Professor Huxley, as the mandible, and so placed in re- 

 lationship to it that it became at once evident that the mandible 

 of Huxley is merely the articular piece, and our supposed man- 

 dible the dentary bone. 



The articular piece is well represented in the memoir referred 

 to. We have three or four isolated specimens of it in a good 

 state of preservation ; also one or two others in connexion with 

 the bones of the head and united to the dentary bone. The ar- 

 ticular piece (PI. XV., fig. 4, a) is long and narrow, with a large 

 arched lobe rising from the upper margin and situated a little 

 nearer to the proximal than the distal extremity ; the proximal 

 extremity is obtusely pointed, and the upper border is occupied 

 by a narrow longitudinal channel (the glenoid surface, b), which 

 widens a little backwards and is twisted or inclined to the exter- 

 nal surface ; the borders of the distal extremity are nearly 

 parallel, and in front it thins out and is diagonally truncated 

 forwards and upwards. Our largest specimen is about two 

 inches and a half long, and at the widest part measures five- 

 eighths of an inch across. 



The dentary bone (fig. 4, c) is as peculiar in form as the arti- 

 cular piece : it is narrow and semicylindrical in front, the outer 

 surface being convex, the inner channeled or concave ; the pos- 

 terior portion, more than half the entire length, widens back- 

 wards, and has the upper and lower borders somewhat thickened ; 

 the proximal extremity thins out, is truncated diagonally down- 

 wards and backwards, and has the lower border, which is the 

 longer, produced into a point. The whole bone is strongly 



