LOWER OLD RED SANDSTONE OF SCOTLAND. 339 



fi sh es of the form ation. I stated further, th at from the existence 

 of two kinds of large coprolites [Spec. 9] in the deposits, — the 

 one traversed by spiral markings, the other by longitudinal 

 strise, — and from several other appearances, I suspected there 

 had been at least one other large fish contemporary with the 

 Asterohpis. Last autumn I satisfied myself that such had 

 been actually the case, and that at least two of the internal 

 bones which I had figured, — mayhap three, — had not be- 

 longed to the Asterohpis. One of the two is, I have con- 

 vinced myself, from the examination of more entire specimens 

 since found, and the study of the head of Diplopterus [Spec. 

 10.], a sphenoid bone of the beam-like type ; and the lateral 

 expansions, which I have described as resembling the barbed 

 portion of the head of an ancient dart or arrow, correspond, 

 I doubt not, to the somewhat similar expansion on the 

 inner or occipital end of the sphenoid bone of the Lepidos- 

 teus. The anterior or vomer end thus broadens and branches 

 out into two forks, and seems to have rested on the interior 

 part of the snout, — the homologue, in some of these ancient 

 fishes, of the vomer. The Diplopterus [Spec. 1 1], as shown by 

 some of my newly-acqaired specimens, possessed a sphenoid 

 bone of tlie beam-like form, which was forked at its anterior 

 termination, and attached its two forks to two crescent-shaped 

 ridges, armed with teeth. The larger sphenoid bones exhi- 

 bited did not, however, belong to the Diplopterus^ but to some 

 unknown fish. Even among these we find varieties of form, 

 which may possibly indicate difierence of species. The sphe- 

 noid bone of the haddock is not more unlike that of the coal- 

 fish or the cod, than one of the fossil sphenoids before us is 

 unlike one of the others. [Spec. 12.] 



There were at least two genera of the Old Red, — the Dip- 

 terus and Aster olepis, — whose skulls were of the broad-based 

 type. The existence of an interesting peculiarity of the ga- 

 noidal head, exemclified in the base of the head of DipteruSf 



