178 DENDIIODUS. 



extinct Dendrodus, as compared with that hitherto known to cha- 

 racterize true fishes, is strikingly manifested both in the extent and 

 regularity of the radiating medullary processes, and more especially 

 in the straight course of the fine and close-set calcigerous tubes 

 which form the intervening dentine. Nevertheless I should most 

 probably have referred these teeth without hesitation to the class 

 of Fishes, if so close an analogy had not been traceable between their 

 singular dental structure, and that still more remarkable modification 

 which will be shown to characterize the extinct Batrachian genus 

 Labyrinthodon. 



If, however, as seems most probable, the Dendrodus be a 

 true fish, we may speculate, from the similarity alluded to, upon its 

 having approached in its general organization, like the Lepidosiren, 

 most closely to the lower confines of the reptilian class : and as this 

 existing annectent genus is aUied to the perennibranchiate Batrachians, 

 so the Dendrodus may have linked some extinct group of the class of 

 Fishes with the equally extinct family of Sauroid Batrachians which 

 we have termed Labyrinthodonts. 



