90 



THE ASTEROLEPIS, 



on these would enable even the most skilful ichthyologist to 

 restore a sixth; nor is the lateral area of the head, whi 

 was, I find, variously occupied in each genus, less difficult t < . 

 restore than the buckler which surmounted it. Two of tlic 

 more entire of these dermal bones I have figured (fig. 44, (i 

 and h) in the hope of assisting future inquirers, who, were 

 Fig 44. 

 1 2 3 



a b 



DERMAL BONES OF ASTEROLEPIS. 



(One-third nat. size, linear.) 

 they to pick up all the other plates, might yet be unable, 

 .acking the figured ones, to complete the whole. The cu- 

 riously-shaped plate a, represented in its various sides by the 

 figures 1, 2, 3, is of an acutely angular form in the trans- 

 verse section (the external surface, 1, forming an angle which 

 varies from thirty to forty-five degrees with the base, 3) ; 

 and as it lay, it is probable, when in its original place, im- 

 mediately under the edge of the cranial buckler, it may have 

 served to commence the line of deflection from the flat top of 

 the head to the steep descent of the sides, just as what are 

 technically termed the spur-stones in a gable-head serve to 

 commence the line of deflection from the vertical outline of 

 the wall to the inclined linp. of the root, or as the spring- 

 stones of an arch serve to commence the curve. A few in- 



