450 



REMARKS ON BATHYGNATHUS BOREALIS. 



narrower than in this genus. The complete relation of the teeth with the jaw in 

 the fossil cannot be clearly ascertained on account of the inner side of both being 

 so intimately imbedded in the sandstone matrix, but, so far as it can be learned, 



the evidence would appear to indicate an arrangement 

 essentially the same as in Megalosaurus and modern Pleu- 

 rodont saurians. 



The mature teeth appear anchylosed with their sock- 

 ets, and they would appear to have been shed and suc- 

 ceeded in the same manner as in the reptiles just men- 

 tioned. 



The fossil is irregularly broken through in the course 

 of the insertion of the largest tooth, viewed as a canine 

 by Prof. Owen, and in this course the arrangement appears 

 to be as represented in the accompanying diagram. The 

 larger tooth, deeply implanted and firmly anchylosed with 

 its socket, has the outer wall of this reaching half an inch 

 lower than the inner wall. Lodged between the latter 

 and the large tooth, protruding from the same alveole, and 

 imbedded in the sandstone matrix, is the summit of a suc- 

 cessional tooth. 



Prof. Owen's paper is accompanied by a wood-cut, 

 representing the fossil of Bathygnathus, taken from the 

 plate accompanying my paper. In the cut the teeth 

 back of the canine are partly numbered as molars, and 

 might give the impression that there were not more than 

 seven, whereas the fossil exhibits positive evidences of a 

 series of nine teeth posterior to the canine. In advance of 

 the latter the fossil contains a small tooth, remaining from 

 a series in this position apparently of three. The small 

 tooth, viewed as an incisor by Prof. Owen, is much worn 

 fore and aft from friction of opposing teeth, leaving some 

 doubt as to whether it accorded in form with the teeth 



behind. It is proportionately less compressed, but exhibits a portion of a back 



trenchant border with a slight trace of crenulation. 



Viewing the fossil as pertaining to the upper jaw, the bone would appear to 



comprise the great part of the maxilla, premaxilla, and nasal, though the limits 



of these I cannot ascertain with any satisfaction. This is rendered the more diffi- 



1. Section of large tooth. 

 2. Its cavity filled with ma- 

 trix. 3. Successional tooth 

 contained in the inner part 

 of the same alveole. 4. Ma- 

 trix. 5. Outer wall of the 

 alveole. 6. Inner wall. 



