DETERMINATION OF FOSSIL TEETH AND BONES 1 09 1 



nature of even the most fragmentary specimens. It was in regard 

 to teeth that the possibility of such determinations was first made 

 clear by the laborious researches of Professor Owen ; l and the 

 following may be given as examples of their value : A rock- 

 formation extends over many parts of Russia whose mineral 

 diameters might justify its being likened either to the Old or to the 

 Xew Red Sandstone of this country, and whose position relatively to 

 other strata is such that there is great difficulty in obtaining 

 evidence from the usual sources as to its place in the series. Hence 

 the only hope of settling this question (which was one of great 

 practical importance, since, if the formation were New Red, coal 

 might be expected to underlie it, whilst if Old Red, no reasonable 

 hope of coal could be entertained) lay in the determination of the 

 organic remains which this stratum might yield ; but unfortunately 

 these were few and fragmentary, consisting chiefly of teeth, which 

 are seldom perfectly pre- 

 served. From the gigan- 

 tic size of these teeth, 

 together with their form, 

 it was at first inferred 

 that they belonged to sau- 

 rian reptiles, in which 

 case the sandstone would 

 have been considered as 

 Xew Red ; but micro- 

 scopic examination of 

 their intimate structure 

 unmistakably proved 



them to belong to a 

 genus of fishes (Dendro- 

 due) which is exclusively 

 palaeozoic, and thus de- 

 cided that the formation 

 must be Old Red. So, 



FIG. 813. Section of tooth of Ldbyrinthodon. 



again, 



the 



microscopic. 



examination of certain fragments of teeth found in a sandstone of 

 Warwickshire disclosed a most remarkable type of tooth-structure 

 (shown in fig. 813), which was also ascertained to exist in certain teeth 

 that had been discovered in the ' Keupersandstein ' of Wiirtemberg ; 

 and the identity or close resemblance of the animals to which these 

 teeth belonged having been thus established, it became almost 

 certain that the Warwickshire and Wiirtemberg sandstones were 

 equivalent formations. The next question arising out of this discovery 

 was the nature of the animal (provisionally termed Labyrinthodon, 

 a name expressive of the most peculiar feature in its dental structure) 

 to which these teeth belonged. They had been referred, from external 

 characters merely, to the order of saurian reptiles ; but it is now 

 clear that they were gigantic salamandroid Amphibia, having many 

 points of relationship to Ceratodus (the Australian mud-fish '), 

 which shows a similar, though simpler, dental organisation. 



1 See his Odontography. 



4 A 2 



