NOTES. 



307 



it is probable, by a weapon of this kind, the head all arotind its eUiptical 

 margin presenting a sharp edge Hke that of a cutting knife or falchion. 

 Its impetus, however, must have been comparatively small, for its organu 

 of motion were so : it was a bolt carefully fashioned, but a bolt cast from 

 a feeble bow. But, if weak in the assault, it must have been formidable 

 when assailed. ' The pointed horns of the crescent,' said Agassiz to the 

 writer, ' seem to have served a similar purpose with the spear-like wings 

 of the Pterichthys,' the sole difference consisting in the circumstance that 

 the spears of the one could be elevated or depressed at pleasure, whereas 

 those of the other were ever fixed in the warlike attitude. And such 

 was the Cephalaspis of the Comstones, — not only the most characteristic, 

 but in England and Wales almost the sole organism of the formation." 

 — (" Old Eed Sandstone," p. 149, et seq.) 



The foregoing description must be understood as applied 

 to the first imperfect impressions of Cephalaspis. Better spe- 

 cimens have been found since, which serve to modify the read- 

 ing or interpretation of these. A gentleman resident in Dun- 

 dee, situated in the Cephalaspian district, furnished the follow- 

 ing note for the latest edition of the Old Red : — 



''Since the foregoing description was written sixteen years ago, a few 

 specimens have been found in the neighbourhood of Arbroath, which de- 

 monstrate that the animal was provided with a large and powerful tail, 

 and with equally powerful pectorals, so that its impetus need not have 

 been, as here stated, * comparatively slow. ' It is now also well ascertained 

 that the peculiar 'cutting knife,' or 'bolt'-like shape of the head, so 

 generally noticeable in the earlier specimens, was the result of accident. 

 A single cephalic shield of bone, thickly covered with discoidal bony 

 plates of beautiful workmanship, was bent round the whole of the upp»r 

 portion of the creature's head, including the sides, somewhat after the 

 fashion of a lady's bonnet shade ; with this difference, that, instead of 

 the pointed ends or ' horns' being fastened, as in the case of the bonnet, 

 they projected freely backwards in the fish. It was altogether, there- 

 fore, an armature of defence, and not partly of offence, as hinted at in the 

 text. Of this Mr Miller had long been quite aware, and, in conse- 

 quence, had expressed himself approvingly of the restoration here given, 

 (fig. 67.) An Arbroath specimen in the possession of Mr Powrie of 

 Reswallie, which shows the head in profile, has the cephalic shield bent 

 round in the manner described. In the large majority of instances, how- 

 ever, the fish being found lying on its belly, the curvature of the shield 

 has yielded to the pressure of the overlying stone, and the appearance of 

 the head is consequently that of a perfectly flat crescent." 



