324 NOTES ON THE STRUCTURE AND RELATIONS 



medium plate, either between the eyes, as in the Coccosteus 

 and Asterolepis, or a very little over them, as in the Osteolepis 

 and Diplopterus ; and remarked that its never-failing recur- 

 rence showed that it must have had some meaning, though 

 it might be difficult to say what. Both gentlemen expressed 

 a desire to see the little plate, as shown in the cranial buckler 

 of the Diplopterus ; and I submitted it to them in a specimen 

 which exhibits it both in the outer and inner surface of the 

 buckler. [Spec. 1 0.] " It is exactly as I had thought," said the 

 distinguished comparative anatomist to Sir Philip ; — " a pro- 

 longation of the brain extended downwards from the brain-pan 

 proper, and bore at its termination the pineal gland, which 

 rested immediately under the little plate, and had its place 

 indicated by it." The revelation struck me as of strange and 

 startling interest. One of the ancients would have said that 

 the ever-recurring little plate which had attracted my notice 

 marked out the exact points where the souls of these ancient 

 fishes of the Old Red Sandstone had their seats. During my 

 late exploratory labours among the rocks of Caithness, I kept 

 the remark of Professor Owen in view, and have succeeded, 

 through the kindness of my friend Mr Dick, in procuring 

 part of a cranium of Diplopterus, which illustrates, and, so 

 far at least as the solid and less perishable parts of an organ- 

 ism can confirm so occult a conclusion regarding the soft and 

 perishable ones, confirms it. In this specimen the occipital 

 and parietal portions of the buckler are removed, showing the 

 brain-pan underneath, and showing also a cavity running from 

 it towards the little plate, and along which a prolongation 

 of the brain seems to have descended. I succeeded also in 

 finding specimens that exhibit the nostrils of Diplopterus ; 

 and a specimen of Asterolepis in which the pineal little plate 

 of this gigantic fish presents its outer side, — a thing which I 

 had attempted restoring in a woodcut from the inner surface ; 

 but though the scope for error in so narrow a field was not 



