a Mandibular Bamus q/' Anthracosaurus Russelli. 75 



nation ; it stood apart, about a quarter of an inch from the 

 second, and as far from the fourth tooth. The fourth and fifth 

 are in contact, and are separated from the sixth by about a 

 quarter of an inch ; the sixth, seventh, and eighth are close 

 together, and form the largest cluster of the series. Then fol- 

 lows a space of upwards of a quarter of an inch, and the series 

 is terminated by three teeth much smaller than the rest ; these 

 are clustered, the first two being almost perfect, and the third 

 {h) having almost entirely disappeared. These three posterior 

 teeth are placed just at the point where the alveolar border 

 begins to rise, and are 2^ inches from the hinder extremity of 

 the specimen. 



The mandible oi Anthracosaurus is distinguished from that 

 of Lo.romma, the only known jaw with wliich it is likely to 

 be confounded, not only by its greater size, but also by the 

 massiveness of the bone. It is an inch deeper or wider than 

 the largest mandible we have seen of the latter ; and the bone 

 is very much thicker. The form of the teeth likewise distin- 

 guishes this species fifom Loxomvia : they have the crown 

 much less compressed, and the trenchant margins are not 

 nearly so much developed ; towards the base, too, they are 

 more cylindrical, or, rather, conical, though they are somewhat 

 irregularly flattened and 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 excep- 

 tion of the three terminal ones of the series. The internal 

 structure of the tooth is also characteristic, and at once distin- 

 guishes 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 upwards, the incurving of the apex, its 

 slight compression and the small development of the trenchant 

 margins 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 

 Anthracosaurus RusseUi j the Labyrinthodont structure in 

 particular accords in every respect with the very clear de- 

 scription 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 Anthracosatirus already 

 quoted, varies according to the state of preservation of the 



6* 



