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 Cœlacanth family. I may mention, however, as a curious subject of inquiry, that the Cœlacanths 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. 33, _c_;) the texture also opens towards the base in the _fish_-teeth, outside, in which, however, the pattern in the transverse section is greatly less complex and ornate than that which the reptile teeth exhibits. When cut across near the point, they appear each as a thick ring, (_b_,) traversed by lines that radiate towards the 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 longitudinal 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 life points, as any portion of the dermal bone on which they rest. [Illustration: Fig. 32. PORTION OF TRANSVERSE SECTION OF REPTILE TOOTH OF ASTEROLEPIS a. _Nat. size._ b. _Mag. twelve diameters._] [Illustration: Fig. 33. A. _Section of Jaw of Asterolepis._ c. _Reptile tooth as shown in section._ a, b, & c. _Row of ichthyic teeth in dermal plate of jaw._ B. _Magnified representatives of ichthyic teeth, a and b, in_ A.]