Fig. 26.—Tail vertebræ of Stegosaurus. (After Marsh.)
1. Side view. 2. Front view.
Finally, the Stegosaur displays a rather remarkable feature; for a very large chamber was found in the sacrum[26] formed by an enlargement of the spinal cord. The chamber strongly resembled the brain-case in the skull, but was about ten times as large! So this anomalous monster had two sets of brains, one in its skull, and the other in the region of its haunches! and the latter, in directing the movements of the huge hind limbs and tail, did a large share of the work. The subject is a highly suggestive one, but at present requires further explanation.
[26] The sacrum may be thus defined: the Vertebræ (usually fused together) which unite with the haunch-bones (ilia) to form the pelvis.
Fig. 27.—Limb-bones of Stegosaurus. (After Marsh.)
1. Fore leg. 2. Hind leg.
On the walls of the fossil reptile gallery at South Kensington the reader will find a large framed drawing of the skeleton of Stegosaurus, kindly sent by Professor Marsh, whose forthcoming monograph will be welcomed by all palæontologists.