100 THE ASTEROLEPIS, 



as the stone which envelopes it Mr Sanderson was, how- 

 ever, surprised to find that the bone of the Asterolepia still 

 retained its elasticity, and was scarce less liable, when heated, 

 to start from the glass, — a peculiarity through which he at 

 first lost several preparations. I have seen a human bone 

 which had for ages been partially embedded in a mass of adi- 

 pocere, partially enveloped in the common mould of a church- 

 yard, exhibit two very different styles of keeping. In the 

 adipocere it was as fresh and green as if it had been divested 

 of the integuments only a few weeks previous ; whereas the 

 portion which projected into the mould had become brittle 

 and porous, and presented the ordinary appearance of an old 

 churchyard bone. And what the adipocere had done for the 

 human bone in this case, seems to have been done for the 

 bone of the Asterolepis by the animal bitumen. 



The size of the Asterolepis must, in the larger specimens, 

 have been very great. In all those ganoidal fishes of the 

 Old Red Sandstone that had the head covered with osseous 

 plates, we find that the cranial buckler bore a cert^ain definite 

 proportion — various in the several genera and species — to 

 the length of the body. The drawing-master still teaches his 

 pupils to regulate the proportions of the human figure by 

 the seven head-lengths which it contains ; and perhaps shows 

 them how an otherwise meritorious draftsman,* much em- 

 ployed about half an age ago in drawing for the wood-engraver, 

 used to render his figures squat and ungraceful by making 

 them a head too short. Now, those ancient ganoids which 

 possessed a cranial buckler may, we find, be also measured by 

 head-lengths. Thus, in the Coccosieus decipiens, the length 

 of the cranial buckler from nape to snout equalled one-fifth of 

 the entire length of the creature from snout to tail. The en- 

 Lire length of the Glyptolepis was equal to about five one-half 



• The late Mr John Thurston. 



