78 



THE ASTEROLEPTS. 



Fig. 35. 



generic name DendroduSy given by Professor Owen to teeth 

 found detached in the deposits of Moray, when the creatures 

 to which they had belonged were still unknown, — a name, 

 however, which will, I suspect, be found synonymous rather 

 with that of a family than of a genus ; for, so far as I have 

 yet examined, I find that the dendrodic or tree-like tooth 

 was, in at least the Old Red Sandstone, a characteristic of all 

 the Celacanth family. I may mention, however, as a curious 

 subject of inquiry, that the Celacanths of the Coal Measures 

 seem to have had their reptile teeth formed of pure ivory, — 

 a substance which I have not yet detected among the reptile- 

 fish of the Old Red. Towards the base of the reptile teeth 

 of Asterolepis, the interstices between the branches greatly 

 widen, as in the branches of a tree in winter divested of its 

 foliage (fig. 35, c) ; the texture also opens towards the base 



in theJ^s^-teeth outside^ 

 in which, however, the 

 pattern in the trans- 

 verse section is greatly 

 less complex and ornate 

 than that which the 

 reptile teeth exhibit. 

 When cut across near 

 the point, they appear 



, , _ ^ . ^ , each as a thick ring 



a, b, and c. How of tchthyic teeth m der- . 



mal plate of jaw. (o), traversed by hues 



B. Magnified representatives of ichthyic tj^^t radiate towards the 

 teeth, a and 6, in A. 



centre ; when cut across 



about half-way down, they somewhat resemble, seen under a 

 high magnifying power, those cast-iron wheels on which the 

 engineer mounts his railway carriages (a). In the longitu- 

 dinal section their line of junction with the jaw is marked 

 by numerous openings, but by no line of division, and they 

 appear as thickly dotted by what were once canaliculi, or 



A. Section of jaw of Asterolepis. 

 c. Reptile tooth as shown in section 



