512 Mr. Owen on the Labyrinthodons 



each groove towards the centre of the dentine, but about the middle of the tooth 

 the enamel disappears, and the convolutions consist of interblended layers of 

 cement and dentine. Thus, on the supposition that the tooth of the Labyrinthodon 

 of the German Keuper be capped with enamel, this constituent of the tooth must 

 have a less extent than in the congeneric tooth from the Warwick sandstone. 



The inflected folds in the Warwick tooth are continued for a greater relative 

 extent before the lateral inflections commence, than in the German species, and 

 the inflections or anfractuosities are rather fewer in number ; some of the inflected 

 converging folds in the Warwick tooth, having nearly reached the central pulp- 

 cavity, are reflected backwards for a short distance before they terminate. 



The modifications of the complex diverging plates of the dentine correspond with 

 those of the tooth of the Labyrinthodon Jcegeri, the observable differences hardly 

 amounting to anything beyond those of a specific character. Thus the peripheral 

 or terminal quadrilateral lobes, as seen in the transverse section, are relatively 

 longer in the Labyrinthodon laniarius, as the Warwickshire species may be pro- 

 visionally termed. 



The number of the inflected folds of enamel at the upper third of the tooth is 

 about forty-five ; such of the folds as nearly reach in the vertical direction to the 

 apex of the tooth extend inwards transversely almost to its centre, and the shorter 

 folds are inflected to an extent proportionate to their length. 



The dentine is composed of calcigerous tubes of the same relative size and dis- 

 position as the Labyrinthodon Jageri. The base of the tooth is similarly anchy- 

 losed to the osseous substance of the jaw. 



In the transverse section of the smaller and relatively broader and shorter co- 

 nical tooth from the Warwick sandstone already mentioned, 1 found, as I had anti- 

 cipated, that the superficial longitudinal striae indicated inflections of converging 

 folds of the external cement as extensive as those in the Labyrinthodon Jesgeri 

 and Labyrinthodon laniarius. They present the same peculiar pattern, being bent 

 from side to side in lateral undulations ; but these are more complicated with nu- 

 merous secondary and tertiary foldings ; I find also that the second and third 

 lateral folds, counting inwards, are the broadest, and that the rest decrease as they 

 approach the centre of the tooth. 



The section was taken from the middle of the portion of the tooth preserved ; 

 this part is not covered by enamel but by cement only, which is relatively thicker 

 than in the Labyrinthodon Salamandro'ides. These differences are sufficiently cha- 

 racteristic of the tooth itself, but whether they indicate a difference of species or of 

 age, or of situation in the jaws of one and the same individual, I cannot at present 

 determine. It may be convenient, however, provisionally to indicate this tooth as 

 belonging to the Labyrinthodon ventricosus. 



It is my intention to prosecute further inquiries into the structure of other teeth 



