134 THE OLD RED SANDSTONE. 
existing varieties with which I am acquainted, it is divided into 
angular sections. The claws nearly resembled those of the 
common lobster; their outline is similar; there is the same 
hawk-bill curvature outside, and the inner sides of the pincers 
are armed with similar teeth-like tubercles. ‘The immense 
shield which covered the upper part of the creature’s body is 
more angular than in the existing varieties, and resembles, 
both in form and size, one of those lozenge-shaped shields 
worn by knights of the middle ages on gala days, rather for 
ornament than use, and on which the herald still inscribes the 
armorial bearing of ladies who bear title in their own right. 
As shown in some of the larger specimens, the length of this 
gigantic crustacean must have exceeded four feet. Its shelly 
armor was delicately fretted with the forms of circular or 
elliptical scales. On all the many plates of which it was 
composed we see these described by gracefully waved lines, 
and rising apparently from under one another, row beyond 
row. They were, however, as much the mere semblance of 
scales as those relieved by the sculptor on the corslet of a 
warrior’s effigy on a Gothic tomb — mere sculpturings on the 
surface of the shell. This peculiarity may be regarded as 
throwing light on the hitherto doubtful impressions of the 
sandstone of Forfarshire — impressions, as has been said, of 
smooth surfaces carved into seeming scales. ‘They occur as 
impressions merely, the sandstone retaining no more of the 
original substance of the organism than the impressed wax 
does of the substance of the seal; and the workmen in the 
quarries in which they occur, finding form without body, and 
struck by the resemblance which the delicately waved scales 
pear to the sculptured markings cn the wings of cherubs — of 
all subjects of the chisel the most common — fancifully termed 
them Seraphim. They have tured out, as was anticipated, 
