316 ME. t. ATTHEY ON ANTHKACOSATJXTJS ItTJSSELLl. 



In another prceinaxilla in my possession, a little smaller than 

 the above, there are five teeth closely set together. The first 

 three are half an inch in length ; the two external or posterior 

 are mnch less. 



The premaxillaries are sntnred behind transversely to the 

 vomers. They are said by Professor Huxley " to send back from 

 their opposed ends two processes which run upwards and back- 

 wards in the middle line (in the manner common in Amphibia) 

 towards the junction of the vomers." These processes do not 

 exist in the above specimen. 



The vomers bear no teeth ; their surfaces, when well preserved, 

 are seen to be covered all over by small pointed tubercles. They 

 are normally united by suture on the median line ; but in 

 Plate VII. they are represented as having been forced asunder 

 by the crushing of the skull. They articulate by suture, in front, 

 with the premaxillaries, and externally with the palate-bones. 

 ]S"ear the base of the great palatine tusk, they form the inner 

 arched sides of the nasal channels. Internal to the tusks the 

 vomers are very narrow, but further back expand a good deal 

 outwards, being all along joined to the inner edges of the palate- 

 bones. They are united behind, next the median line, with the 

 pterygoids. 



The nasal channels are directed from the external orifices in- 

 wards and backwards towards the median line ; for two inches 

 of their course they are well defined, and measure half an inch 

 in breadth. They are 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 Professor Huxley, in " Quart. Journ. 

 Geol. Soc." Vol. XIX. p. 59, fig. 1, 1863, as the anterior palatine 

 foramen. 



In the plates annexed to the Report of the Committee of the 

 British Association on the Structure and Classification of the 

 Labyrinthodonts, 1874, namely, in Plate IV., fig. 2 (Mastodon- 

 saurus), Plate IV., fig. 4 (Trematosaurus), and Plate VI., fig. 4 

 (Archcgosaurus), the posterior nares are indicated at a short 



