154 ^Ir. T. Atthey on Authracosaurus Kusselli. 



breadth. They arc bounded internally by the vomers, and 

 behind by the palate-bones. Their upper surface is formed by 

 the nasals ; and they appear open below, but would doubtless 

 be closed in during life by membrane, cartilage, or bone. 

 One of these openings is noticed by Prof. Huxley, in * Quart. 

 Journ. Geol. Soc.' vol. xix. p. 59, tig. 1, 1863, as the anterior 

 palatine foramen. 



In the plates annexed to the lleport of the Committee of 

 the British Association on the Structure and Classification of 

 the Labyrinthodonts (1874) — namely, in plate iv. fig. 2 {Mas- 

 todonsaurus) , plate iv. fig. 4 {Trematosanrus) , and plate vii. 

 fig. 4 {Arcfiegosaurus) — the posterior nares are indicated at a 

 short distance behind the external nasal orifices, internal to and 

 very near the outer margin of the cranium, though internal to 

 the maxillary bone ; whereas in Authracosaurus the channel 

 from the external nasal orifices leads inwards and backwards 

 towards the middle line, and appears to have been carried 

 further backwards under the pterygoids to near the posterior 

 end of the presphenoid. 



The large palatine foramen of the above-named Labyrintho- 

 donts does not exist (as already noticed) in Anthracosaurus. 



With respect, however, to the backward position of the nares, 

 it may be as well to leave this for the present an open question, 

 until a specimen is found with the bones of the under surface 

 of the skull better disposed for advantageous observation. With 

 all the respect due to the opinion of so learned and skilful a 

 palaeontologist as Professor Huxley, my humble opinion is that 

 the posterior nares will be found as far back as the posterior 

 end of the presphenoid. 



Indeed I may add that I have a very interesting specimen, 

 comprising the whole of the right nasal bone oi Anthracosaurus ^ 

 showing both the upper and under surfaces, and measuring 4 

 inches in length. The external angle of its anterior end shows 

 a part of the margin of the external nasal orifice ; and the roof 

 of the channel leading inwards and backwards from it is 

 distinctly visible along the whole length of the bone. Now, 

 as no opening exists on the under surface of the roof of the 

 mouth, the nasal channel must be continued on to the back 

 of the palate. 



The right maxilla is narrow and 11^ inches long, and ex- 

 tends from the prtemaxilla to 2g inches from the posterior angle 

 of the quadrate-jugal. It bears 15 teeth. For 3 inches at 

 the anterior end there are no teeth visible, owing to the right 

 ramus of the mandible lying over them. Behind this space 

 the position of six teeth can be made out ; they are t% inch 

 apart, and are all broken, but project nearly through the man- 



