388 MESSES. HANCOCK AND ATTHEY ON A 



angulated at the sides. They are also much more uniformly of 

 a size ; in this respect they vary greatly in Loxomma, while we 

 have seen that in the fragment before us the teeth are about the 

 same length, with the exception of the three terminal ones of 

 the series. The internal structure of the tooth is also character- 

 istic, and at once distinguishes this species from Loxomma. 



Indeed, the characters of the teeth of Anthracosaurus are very 

 peculiar ; their thickness and angularity at the base, the delicate 

 conical taper outwards, the incurving of the apex, its slight 

 compression and the small development of the trenchant mar- 

 gins are the distinguishing features of this form, and at once 

 enable us to determine the generic and specific identity of Mr. 

 Ward's interesting fragment. But had any doubt existed, the 

 internal structure of the tooth would have removed it. In all 

 these characters this specimen exactly agrees with Anthracosau- 

 rus Russelli ; the Labyrinthodont structure in particular accords 

 in every respect with the very clear description given of it by 

 Professor Huxley in the original memoir. 



It is true that the teeth are stated to be ridged, while we have 

 described them as grooved. This character, however, we pointed 

 out, in our former paper on Anthracosaurus already quoted, va- 

 ries according to the state of preservation of the specimen. We 

 have in our possession teeth of this species both ridged and 

 grooved. They seem to vary in this respect even when per- 

 fectly fresh ; but if a little eroded, the ridges are much exagge- 

 rated and become quite sharp, giving a very striking appearance 

 to the tooth. In Loxomma the same variability obtains : the 

 teeth of that form are usually grooved ; some, however, are 

 ridged, while in others the ridges are greatly increased by ero- 

 sion. 



There is in Mr. Atthey's collection a peculiar bone from the 

 shale at Newsham, that has been a great puzzle to us for a long 

 time. It was not till a nearly perfect mandibular ramus of 

 Loxomma was obtained that its true nature was solved. It was 

 then at once seen to be the articular piece, with a portion of 

 the dentary bone attached, of some large Labyrinthodont. In 

 form it closely resembles the same part in the ramus just alluded 



