LOWER OLD RED SANDSTONE OP SCOTLAND. 345 



bone laid along the upper edge of the jaw, and set thick with 

 ichthyic teeth. A curiously shaped bone, which must, from 

 its form, have occupied a medial place in the jaw to which it 

 belonged, and which bears the dermal markings of the un- 

 known fish, formed in all probability a central key in the 

 creature's nether jaw. [Spec. 24.] The provision seem* a 

 curious one. And yet, strange as such a structure of jaw must 

 be deemed, it was not by any means the strangest furnished 

 by the Old Red Sandstone. 



It is the under jaw of the Coccosteus that must be regarded 

 as the most extraordinary of the period, — ^perhaps of any pe- 

 riod. It consisted of two bones, — one on each side, — which 

 were furnished each with its group of from five to eight teeth, 

 placed exactly where in the human subject the molars occur. 

 And these groupes seem to have acted against corresponding 

 groupes in the upper jaw. But at right angles with these 

 molar groupes, exactly in the symphysis, there was another 

 group of teeth from three to five in number ; and these, so 

 far as appears, could not have acted against teeth placed in 

 the upper jaw, but were directly opposed, the terminal group 

 in the one bone that formed the half jaw, to the terminal 

 group in the other jaw. [Spec. 25.] I called the attention of 

 palaeontologists, about nine years ago, to something veiy pe- 

 culiar in the jaws of Coccosteus, and solicited inquiry respect- 

 ing them ; but the restoration of Agassiz, who had been mis- 

 led by imperfect specimens, several of them derived from my 

 own collection, had been regarded as determining the point 

 against the peculiarity ; and it was only during the last sea- 

 son that I was enabled to demonstrate from newly-found Coc- 

 costei that it in reality existed. One of the best of these I 

 owe to a lady of Cromarty, Mrs James Hill, — an intelligent 

 geologist and successful collector. [Spec. 26.] The teeth of the 

 Coccosteus J viewed as prepared transferences in the microscope, 

 somewhat resemble those of a Hyhodus of the Oolite, which I 



