332 ME,. T. ATTHEY ON ANTHKACOSATTItUS ETJSSELLI. 



Three crania of Pteroplax (one in the Leeds Museum and two 

 in my cabinet) are all we know as yet of this rare amphibian. On 

 one of these latter lie two ribs which most probably belonged to 

 the same animal. That on the upper surface is entire and much 

 like a rib of Loxomma, but smaller ; both head and tubercle are 

 well shown : that on the under surface cannot well be described, 

 as it is not sufficiently exposed. All three specimens are from 

 Newsham, near Myth, Northumberland. 



The general configuration of the under surface of the skull is 

 much the same in Loxomma and in Anthracosaurus, but is very 

 different in Pteroplax. The vomers pass much further forward 

 in Anthracosaurus than in Loxomma. Their anterior margins 

 in the latter are just in front of the vomerine tusks, and are 

 sutured to each other on the median line : by their outer mar- 

 gins they join the maxillaries, and behind the palate-bones; 

 whilst in Anthracosaurus the anterior end of the palate-bone 

 lies in between the vomers and the maxillaries. The posterior 

 part of the palate is much the same in Anthracosaurus and Lox- 

 omma, but, so far as I can ascertain, is probably very different 

 in Pteroplax. 



Whether Anthracosaurus possessed epiotic horns like Loxomma 

 and Pteroplax is not determinable, the specimen being deficient 

 at these parts. 



The teeth of Anthracosaurus differ much from the teeth of 

 Loxomma ; they are slightly oval in outline and altogether 

 stronger than the latter, which are much flattened. The teeth 

 of both in section show most beautiful Labyrinthodont struc- 

 ture. The teeth of Pteroplax have not as yet been found. 



The vertebrae and ribs in Anthracosaurus and Loxomma are 

 of large size, very strong, and most difficult to distinguish from 

 each other when found separate, None of the vertebrae of 

 Pteroplax have ever been discovered. 



The drawings which accompany this paper, and also those il- 

 lustrating the paper on Loxomma, are from the accurate pencil 

 of Mr. William Dinning of this town, whose kind assistance is 

 here gladly acknowledged. 



