198 LABYRINTHODONTS. 



to the same genus as the Batrachians of the Warwick Sand- 

 stones, and, therefore, I shall hereafter describe the German species 

 under the name of Labyrinthodon Jaegeri. 



As the circumstances which led me to detect this generic identity 

 strikingly illustrate the value of the microscopic structure of teeth 

 as a distinctive and available test of the nature and affinities of an 

 extinct species, expecially in the absence of any other character, I 

 shall here premise the account of these investigations as communi- 

 cated by me to the Geological Society of London. (1) 



A question was at issue whether the light coloured sandstone of 

 Warwick was the equivalent of the Keuper or the Bunter division of 

 the New-Red Sandstone formation as developed in Germany, and its 

 decision had been set by one of the contending geologists upon the 

 issue of organic remains, more especially of the supposed Saurian 

 fossils of the strata in question. "If it could be shown," said the 

 able supporter of the ' Bunter' theory, " that the fossils which we 

 have pointed out as characterizing the upper sandstone occurred also 

 in the lower, and that the fragments of Saurians formed in the 

 sandstone of Guy's Cliff and Warwick really belonged to the species 

 peculiar to the Keuper, then, indeed, we should willingly allow that 

 the lower sandstone also must be grouped with that formation." 



" In respect to the Saurian of Guy's Cliff, which we have had 

 no opportunity of examining, it is sufficient to state, that Dr. Buck- 

 land himself does not contend that it is either of the species of the 

 Phytosaurus (Jaeger) of the German Keuper ; and he hesitates even 

 to refer it to that genus. Now the mere existence of a Saurian in the 

 Warwick sandstone proves nothing ; for Geologists are well aware 

 that various species of the family occur in all the formations, from the 

 lias down to the magnesian lime-stone inclusive." (2) 



The reptilian remains figured by the authors above quoted from 

 the lower or Warwick sandstone were a few teeth or rather fragments 

 of teeth, and a portion of a vertebra : and these were the fossils to 

 be compared with the reptiles peculiar to the German Keuper. 



(1) Proceedings of the Geological Society, January 20th, 1841. No. 74, p. 257- 



(2) " On the Upper Formations of the New Red Sandstone System in Gloucestershire, Wor- 

 cestershire and Warwickshire, &c., by R. I . Murchison, Esq. V.P. G.S., and H. E. Strickland, 

 l^sq., F.G.S." — Geological Transactions, vol. v, 2d Series, p.p. 345, 346, PI. 28 and 29- 



