306 



NOTES. 



Fig. Q6. 



comprising fully one-third the creature's entire length. In the centre, 

 and placed closely together, as in many of the flat fishes, were the eyes. 



Some of the specimens show two dor- 

 sals, and an anal and caudal fin. The 

 thin and angular body presents a joint- 

 ed appearance, somewhat like that of a 

 lobster or trilobite. Like the bodies of 

 most of the ichthyolites of the system, 

 it was covered with variously-formed 

 scales of bone ; the creature's head was 

 cased in strong plates of the same mate- 

 rial, the whole upper side lying under 

 one huge buckler ; and hence the name, 

 — Cephalaspis or buckler-head. In pro- 

 portion to its strength and size, it seems 

 to have been amply furnished with wea- 

 pons of defence. Such was the strength 

 and massiveness of its covering, that its 

 remains are fomid comparatively entire 

 in arenaceous rocks impregnated with 

 iron, in which few other fossils could 

 have survived. * Its various species, 

 as they occur in the Welsh and English 

 cornstones,' says Mr Murchison, * seem 

 not to have been suddenly killed and 

 entombed, but to have been long ex- 

 posed to submarine agencies, such 

 as the attacks of animals, currents, 

 concretionary action,' &c. ; and yet, 

 'though much dismembered, the geo- 

 logist has little difficulty in recognising even the smallest portions of 

 them.' Nor does it seem to have been quite unfurnished with offensive 

 weapons. The sword-fish, with its strong and pointed spear, has been 

 known to perforate the oaken ribs of the firmest built vessels, and, poised 

 and directed by its lesser fins, and impelled by its powerful tail, it may 

 be regarded either as an arrow or javelin flung with tremendous force, 

 or as a knight speeding to the encounter with his lance in rest. Now, 

 there are missiles employed in eastern warfare, which, instead of being 

 pointed like the arrow or javelin, are edged somewhat like the crooked 

 falchion or saddler's cutting knife, and which are capable of being cast 

 with such force, that they have been known to sever a horse's leg through 

 the bone ; and if the sword-fish may be properly compared to an arrow 

 or javelin, the combative powers of the Cephalaspis may be illustrated, 



Cephalaspis Lyelli, — Ayassiz. 



