76 



THE ASTEROLEPIS, 



of the exterior plate as iron spikes on the upper edge of a 

 gate (fig. 32). Mr Parkinson expresses some wonder, in Lis 

 Virork on fossils, that, in a fine ichthyolite in the British Mu- 

 seum, not only the teeth should have been preserved, but also 

 the lips ; but we now know enough of the construction of 

 the ancient ganoids to cease wondering. The lips were 

 formed of as solid bone as the teeth themselves, and had as 

 fair a chance of being preserved entire ; just as the metallic 

 rim of a cogged wheel has as fair a chance of being preserved 

 as the metallic cogs that project from it. Immediately be- 

 hind the front row, — in which the teeth present the ordinary 

 ichthyic appearance, — there ran a thickly-set row of huge rep- 

 tile teeth, based on an interior platform of bone, which formed 

 the top of the cartilage-enclosing box composing the jaw. 

 These were at once bent outwards and twisted laterally, some- 

 what like nails that have been drawn out of wood by the 

 claw of a carpenter's hammer, and bent awry with the wrench 

 (fig. 33). They were furrowed longitudinally from point to 



Fig. 33. 



POBTION OF UNDER JAW OP ASTEROLEPIS (INNER SIDE). 



(One-haJf nat. size.) 



case by minute thickly-set strise ; and were furnished late- 

 rally, in most of the specimens, though not in all, with two 

 sharp cutting edges. The reptile had as yet no existence in 

 creation j but we see its future coming symbolized in the den- 



