i 2 THE ASTEROLEPIS, 



ening of the buckler which takes place along their line is at 

 least as much a consequence of their inner as of their outer 

 elevation over the general platform. A fourth bar ran trans- 

 versely along the nape, and formed the cross beam on which 

 the others rested ; for the three longitudinal ridges may be 

 properly regarded as three strong beams, which, extending 

 from the transverse beam at the nape to the front, where they 

 converged like the spokes of a wheel at the nave, gave to 

 the cranial roof a degree of support of which, from its great 

 flatness, it may have stood in need. In cranial bucklers in 

 which the average thickness of the plates does not exceed 

 three eighth parts of an inch, their thickness in the centre of 

 the ridges exceeds three quarters. The head of the largest 

 crocodile of the existing period is defended by an armature 

 greatly less strong than that worn by the Asterolepis of the 

 Lower Old Bed Sandstone. Why this ancient ganoid should 

 have been so ponderously helmed we can but doubtfully 

 guess : we only know, that when nature arms her soldiery, 

 there are assailants to be resisted, and a state of war to be 

 maintained. The posterior central plate, the homologue ap- 

 parently of the occipital bone, was curiously carved into an 

 ornate massive leaf, like one of the larger leaves of a Corin- 

 thian capital, and terminated beneath, where the stem should 

 have been, in a strong osseous knob, fashioned like a pike- 

 head. Two plates immediately over it, the homologues of 

 the superior frontal bone, with the little plate which, perched 

 atop in the middle, lay between the creature's eyes, resem- 

 bled the head and breast in the female figure at least not 

 less closely than those of the " lady in the lobster ;" the pos- 

 terior frontal plates in which the outer and nether half of the 

 eye-orbits were hollowed formed a pair of sweeping wings ; 

 and thus in the centre of the buckler we are presented with 

 the figure of an angel, robed and winged, and of which the 

 large sculptured leaf forms the body, traced in a style in no 



