140 Proceedings of the Boyal Physical Society. 



the posterior laniaries are present; but being imbedded in 

 hard ironstone, the surface of the bone is so injured as 

 to render recognition of sutures a matter of difficulty ; they 

 show, however, very clearly that these posterior laniaries 

 are implanted in a thickened ledge, somewhat nodulously 

 enlarged round the base of each, and continuing backwards 

 the symphysial thickening of the dentary proper — this ledge 

 with its teeth being totally absent in the detached den- 

 taries above alluded to. I now selected for special prepa- 

 ration two jaws, seen from the outer surface, and fortunately 

 imbedded in a rather soft laminated clay. The first of 

 these was a portion of a comparatively small jaw, 3^ inches 

 in length, and broken across f inch behind the stump of 

 the second laniary; and by softening the matrix with water, I 

 succeeded in completely detaching it and cleaning its inner 

 surface. The surface of the bone being here quite intact, I 

 obtained a clear proof of the fact which I had anticipated, viz., 

 that the second laniary tooth is attached to a separate piece of 

 bone articulated by a distinct suture to the anterior thickening 

 of the dentary, and having its outer surfice in apposition 

 with the flat inner surface of the dentary behind that thicken- 

 ing. The next jaw was a larger one, measuring 14 inches in 

 length, showing three entire laniaries and the stump of a 

 fourth, the articular extremity being, however, unfortunately 

 broken off. Having covered up the outer surface of the speci- 

 men with a sufficient mass of Portland cement, I turned it 

 over and worked down upon it from the other side, the prepa- 

 ration thus obtained entirely corroborating the conclusions pre- 

 viously arrived at. The large teeth are seen to be borne upon 

 a thickened ledge, diminishing in strength from before back- 

 wards, the anterior part of which is the previously described 

 symphysial thickening of the dentary proper, and carries the 

 first great laniary ; the suture between that and the anterior 

 of the accessory internal dentary pieces bearing the second 

 laniary is distinctly seen ; but posteriorly the separation of the 

 others is obscured by the obstinate adherence to the bone of a 

 thin layer of the matrix, which cannot be thoroughly cleared 

 off without injuring the surface. My attention w^as next 

 directed to a block of the same laminated clay containing 



