54 THE OLD RED SANDSTONE. 
than ever. Its repetition here, however, will, I trust, be regarded as 
simply indicative of a wish on the part of the writer, that the ques- 
tion be kept open just a little longer, and that further examination be 
made. There is certainly something very peculiar about the mouth 
of the Coccosteus not yet understood, and singularly formed plates, 
connected with it, which have not been introduced into any restora- 
tion, and the use of which in the 
economy of the animal seem wholly 
unknown. [1850.—TI have at length 
found a very perfect specimen of the 
nether jaw of Coccosteus, and am pre- 
pared to show that it was of a char-. 
acter altogether unique. It had its 
two groups of from six to eight teeth, 
(exactly where, in the human sub- 
ject, the molars are placed,) that 
seem to have acted on correspond-_ 
ing groups in the intermaxillaries, 
and two other groups of from three 
to five teeth placed at right angles 
with these, direct in the symphysis, 
and that seem to have acted on each 
other. But though these unique teeth of the symphysis formed a ver- 
tical line of mouth, it joined on at right angles to a transverse line of 
the ordinary type, as the upright stroke of the letter T joins on to the 
horizontal line a-top.] Fourth edition, 
