ON A LABYRINTHODONT AMPHIBIAN. 217 



seem to be united to the prsemaxilla ; it has likewise all the ap- 

 pearance of having been free. 



In the less perfect specimen, as before mentioned, the pras- 

 maxilla of the left side is pressed inwards in the same manner 

 as that of the right side in the other specimen ; and both agree 

 in having seven teeth, and in having had apparently the posterior 

 extremity free. From these coincidences it would seem fair to 

 assume that the prsemaxillaa comprise the whole of the bony 

 structure of the upper jaw. At the same time it must be allowed 

 that, as previously pointed out, the row of teeth on the left side 

 of the vomer in one of the specimens has much the appearance 

 of having belonged to a maxilla ; and if this should prove to be 

 the case, then Batrachiderpeton would be more closely allied to 

 Axolotl than to Siren. 



In the large size of the coronal bones, Batrachiderpeton also 

 shows an alliance with Siren and Axolotl, while, in the square- 

 ness of the occipitals and parietals, it agrees with the Salamander 

 and the Batrachians. But, notwithstanding these deviations 

 from the usual characters, there can be little doubt that our new 

 form is a true Labyrinthodont ; for the lateral cranial expan- 

 sions, though more developed than commonly, are very similar 

 to those characteristic features of these amphibians. And the 

 parietal foramen is most significant, as well as the stoutness of 

 the teeth ; and the row of strong vomerine teeth on each side is 

 also characteristic. 



But this is not the only instance in which a Labyrinthodont 

 has been found to exhibit an approximation to the Siren-ty-pe of 

 structure. Pteroplax is so related, as we have pointed out in 

 the May number of the "Annals." At present, however, it is 

 not necessary to dilate further on this matter than to state that 

 Pteroplax seems to approach Siren in a different line from that 

 by which it is approximated by Batrachiderpeton. In the former 

 the lateral cranial expansions of the Labyrinthodont are entirely 

 reduced, while in the latter they are even exaggerated in extent ; 

 and in Pteroplax, again, the coronal bones are not much altered 

 in form, and the frontals are very long, showing that the muzzle 

 was much produced. In Batrachiderpeton, on the contrary, the 



