ITS STRUCTURE, BULK, AND ASPECT. 85 



outline from tliat of a specimen of Professor Asmus, of which 

 a cast may be seen in the British Museum ; while the shaded 

 portion represents the fragment found by Mr Dick. The 

 intermaxillary bones, like the dermal plates of the lower jaw, 

 were studded by star-like tubercles, and bristled thickly along 

 their lower edges with the ichthyic teeth, flanked by teeth of 

 the reptilian character. The opercules of the animal consist- 

 ed, as in the sturgeon, of single plates (fig. 39) of great mas- 

 si ven ess and size, thickly tubercled ^. 



. -, . 1 ,. . . Fig. 39. 



outside, without trace of joint or su- 

 ture, and marked on their under sur- 

 face by channelled lines, that radiate, 

 as in the other plates, from the centre 

 of ossification. That space along the 

 nape which intervened between the 

 opercules, was occupied, as in the 

 Dipterus and Diplovterus, by three inner surface of oper- 



/^ 1 1 -I CULUM OP ASTEROLEPIS. 



plates, which covered rather the an- 



. . ,. /. ,1 1 1 .1 .1 (One-fifth nat. size, linear.) 



tenor portion of the body than the 



posterior portion of the head, and which, in the restoration 

 of Osieolepis (fig. 1 3), appear as the plates, 9, 9, 9. I can 

 say scarce anything regarding the lateral plates which lay 

 between the intermaxillaries and the cranial buckler, and 

 which exist in the Osteolepis, fig. 1 3, as the plates 2, 4, 5, 6, 

 and 7 ; nor do I know how the snout terminated, save that 

 in a very imperfect specimen it exhibits, as in the Diplopterua 

 and Osteolepis, a rounded outline, and was set with teeth. 



That space comprised within the arch of the lower jaws, 

 in which the hyoid bone and branchiostegous rays of the os- 

 seous fishes occur, was filled by a single plate of great size and 

 strength, and of singular form (fig. 40) ; and to this plate, 

 existing as a steep ridge running along the centre of the in- 

 terior surface, and thickening into a massy knob at the an- 

 terior termination, that nail-shaped organism which I have 



