184 WALKS AND TALKS. 



Aspidichthys belonged also to a bony plated fish as large as 

 Dinichthys; but its plates, as far as known, are covered with 

 large, hemispherical, smooth, enameled tubercles. 



In the Corniferous Limestone we find also quite numerous 

 bones and teeth of fishes. They all belong, however, to those 

 orders which include the modern Sharks and Gar-Pikes or 

 Ganoids. No trace of soft-scaled fishes is certainly known 

 below the Mesozoic. Some of these sharks had enormous 

 bayonet-like spines inserted in front of certain of their fins ; 

 and the Ganoids were armed with strong, conical teeth, and 

 protected by bony enameled scales. 



Every one has read or heard of the " Old Red Sandstone." 

 In some parts of this Scottish formation were found fish re- 

 mains which Miller described years ago, in a popular and fas- 

 cinating style which attracted much attention. This was one 

 of the earliest attempts to interest the public in fossil remains 

 and we might even add, in any branch of geology. Hugh 

 Miller was a mere quarryman, and Agassiz was so surprised to 

 find such a man doing good work in science, that his praise 

 contributed much to Miller's fame. The renowned fishes of 

 Scotland were mostly Placoderms, like Dinichthys. One of 

 them has been called Ceph-al-as'-pis (shield-head), for it had a 

 broad flattened head shaped like a saddler's knife in outline, 

 with a tapering conical body. Another is Pter-ich'-thys 

 (winged fish) since its only fins stood out at right angles like 

 wings. But no European fishes possess any greater interest 

 than our own. 



XXXII. ANCESTRY OK THE PEARLY NAU- 

 TILUS. 



SILURIAN REMAINS. 



THE Pearly Nautilus still lives in the deep waters of trop- 

 ical seas. This is not the Paper Nautilus or Fairy Sailor, of 

 which Byron wrote: 



" The tender Nautilus who steers his prow 

 The sea-born sailor of his shell canoe. 



