476 LOUIS AGASSIZ. 



and face of the effigy in the centre of the 

 buckler, and a side-plate, into which the 

 condyloid processes of the lower jaw were 

 articulated, and which exhibited the processes 

 on which these hinged. There are besides 

 some two or three plates more, whose places I 

 have still to find. The small cast, stained yel- 

 low, is taken from an instructive specimen of 

 the jaws of coccosteus, and exhibits a peculiar- 

 ity which I had long suspected and referred 

 to in the first edition of my volume on the 

 Old Red Sandstone in rather incautious lan- 

 guage, but which a set of my specimens now 

 fully establishes. Each of the under jaws of 

 the fish was furnished with two groups of 

 teeth : one group in the place where, in quad- 

 rupeds, we usually find the molars ; and an- 

 other group in the line of the symphyses. 

 And how these both ^could have acted is a 

 problem which our anatomists here many of 

 whom have carefully examined my specimen 

 seem unable, and in some degree, indeed, 

 afraid to solve. 



I have written to the Messrs. Gould, Ken- 

 dall & Lincoln to say that the third edition 

 of the " Footprints " differs from the first and 

 second only by the addition of a single note 

 and an illustrative diagram, both of which I 



