FOSSIL FISHES. 



21 



from the Devonian of N. America, the dentition of which greatly 

 resembles that of the recent Protopterus (Fig. 35) ; Dr. Traquair 

 is of opinion that the Placodermata may turn out to have been an 

 aberrant group of loricated Dipnoi. 



■«5>\\\ 



Fig. 29. — Coccosttu.s decipiens (dorsal aspect). Agassiz. 



The Ceplialaspirfce (Table-case 35) includes a peculiar and very 

 ancient group of Palaeozoic fishes, limited to the Upper Silurian 

 aud Old Red Sandstone. 



Fig. 30. — Cephalaspis Li/elli (restored), side-view (after Lankester), Old Red Sandstone, 

 Forfarshire (drawn about one-third natural size). 



The earliest (Scapliaspis ludensis) is from the Lower Ludlow 

 rock, near Ludlow, the oldest known fish. The head is covered 

 with a large buckler composed of one or more pieces, a tail covered 



Fig. 31. — CepTialaspis Lyelli (dorsal aspect), from the Old Red Sandstone, Glammis, Forfar- 

 shire (about one-third the size of the original specimen). ", < hie of the peculiar ornaments 

 (drawn natural size) with which the head is covered wh<m the .surface of the headshield is 

 preserved ; b and c, scales from different parts of the body and tail. 



with rhombic scales; but no internal skeleton of any kind has been 

 met with. 



