ITS STRUCTURE, BULK, AND ASPECT. 69 



The creature's cranial buckler, which was of great size and 

 strength, might well be mistaken for the carapace of some Che- 

 Ionian fish of no inconsiderable bulk. The cranial bucklers of 

 the larger Dipterians were ample enough to have covered the 

 corresponding part in the skulls of our middle-sized market- 

 fish, such as the haddock and whiting ; the buckler of a Coc- 

 costeus of the extreme size would have covered, if a little 

 altered in shape, the upper surface of the skull of a cod ; but 

 the cranial buckler of Asterolepis, from which the accom- 

 panying woodcut was taken (fig. 28), would have considerably 



Fig. 28. 



h a b 



CEANTAL BUCKLER OF ASTEROLEPIS. 



(One-fifth nat. size, linear.) 



more than covered the corresponding part in the skull of a 

 large horse; and I have at least one specimen in my collec- 

 tion whicL would have fully covered the front skull of an 

 elephant. In the smaller specimens, the buckler somewhat 

 resembles a labourer's shovel divested of its handle, and sorely 

 rust eaten along its lower or cutting edge. It consisted of 



