OP THE EARLIER GANOIDS. 321 



helmet, and the upper part of its body with a strong cui- 

 rass of osseous plates, its nether parts were naked. And 

 along the space once occupied by this naked part we find 

 frequent traces in the rock of the internal osseous mechanism 

 which protected the spinal cord, — a mechanism which I have 

 never yet seen in any of the other ichthyolites of the forma- 

 tion. I have been accustomed to account for this peculiarity 

 in the Coccosteus, on the supposition that, as its naked part 

 had no such external support as that furnished to the poste- 

 rior portions of its contemporaries by the strong osseous scales 

 and plates with which they were covered, it was furnished, 

 on that compensatory principle so common in the animal 

 world, with a proportionally stronger skeleton within; nor 

 have I found reason to alter this view. I had further sup- 

 posed, however, that though the apophyses of the vertebral 

 column of Coccosteus were more thoroughly ossified than the 

 vertebrae themselves, and were preserved in some kinds of 

 rock from which the vertebrae had disappeared, the creature 

 actually had vertebral joints of bone, and that they were ex- 

 hibited in some of my specimens.* I, however, succeeded 

 in convincing myself, during my exploratory ramble in au- 

 tumn last, that what I had deemed vertebrae are in reality 

 curiously-formed apophyses, that, linked into each other by a 

 sort of male and female joints, threw out slender processes 

 on their outer sides, and ran adown the back in double 

 column along the neural cord. So far as we now know, no 

 ganoid of the Old Ked Sandstone possessed vertebral joints 

 of bone. Among the specimens of Coccosteus on the table, 

 there are several very interesting ones, illlustrative of parts 



* These remarks upon the vertebral structure of the Coccosteus are ex- 

 ceedingly interesting, when viewed in connection with Professor Huxley's 

 recent investigations ; and likewise when read in the light of Mr Peach's 

 discovery of ossified vertebral columns in some of the fishes of the Old 

 Red. -L. M. 



I. 



