368 Proceedings of the British Association for 1850. 



tion from M. Martins on " Parallele entre les Terrains 

 superficiels du basin Suisse et de la Plaine dii Po." 



Professor Oldham made some additional remarks on the 

 temperature of mines in Ireland, to the effect that, in the 

 very same lode, they had in the shallow portion one degree 

 for every fifty-two feet ; but at a depth of twelve hundred 

 feet, they had a rise of one degree for every eighty-five 

 feet. 



Mr Hugh Miller then made a communication on certain 

 peculiarities of structure in the more ancient ganoids. 

 Mr Miller began by stating that it was his purpose to 

 introduce to the notice of the Association a curious suite 

 of fossils from the Lower Old Red Sandstone of Scot- 

 land, many of which were still without duplicate in the public 

 museums of the empire, and but imperfectly represented in 

 those of Russia. In one important respect there attached 

 to them a peculiar interest. They belonged to the earliest 

 animals of the vertebral division, of which our knowledge 

 was rather inferential than direct. The most ancient fishes 

 known to the geologist were the Placoids of the Silurian 

 System ; the next most ancient the Placoids and Ganoids 

 of the Lower Old Red Sandstone. Of the placoids, however, 

 little comparatively could be known ; from their perishable 

 cartilaginous structure an entire species might be repre- 

 sented by but a few spines, teeth, or shagreen points ; 

 whereas the ganoids, from the peculiar armature of solid 

 bone in which they were enveloped, continued to exist, not 

 as mere ichthyic fragments, but as ichthyolites. Hence our 

 absolute knowledge of the ancient forms and mechanism of 

 ichthyic life was mainly to be derived from the study of the 

 first ganoids. Mr Miller submitted to the Society several 

 specimens. In a Dura Den specimen of Pterichthys^ for ex- 

 ample, the very capsules of the eyes were preserved ; and 

 we had evidence of at least the three senses with which these 

 earliest of the ganoids took note, in an incalculably remote 

 period, of the sights, sounds, and odours of the material 

 world. 



Dr Anderson read a paper on the Fossil Fishes and the 

 Yellow Sandstone of Dura Den. 



