DETERMINATION OF FOSSIL TEETH. 



763 



tion extends over many parts of Russia, whose mineral characters 

 might justify its being likened either to the Old or to the New 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 preserved. From the gigantic size of these Teeth, 

 together with their form, it was at first inferred that they belonged 

 to Saurian Reptiles, in which case the Sandstone must have been 

 considered as New Red; but Microscopic examination of their 

 intimate structure unmistakably proved them to belong to a genus 

 of Fishes (Dendrodas) which is exclusively Palaeozoic, and thus 

 decided that the formation must be Old Red. — So 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. 407), which was also ascertained to 



Fig. 407. 



Section of Tooth of Labyrinthodon. 



exist in certain Teeth that had been discovered in the ' Keuper- 

 sandstein' of "Wirtemberg ; and the identity or close resemblance 



