[17] In August, 1892, Mr. Dollo wrote, in answer to inquiries from South Kensington, to say that five are already mounted and exhibited, and five more are almost ready for mounting. He also stated that the remains represent twenty-nine individuals, not twenty-three, as above. [18] _Geological Magazine_, January, 1885. The specimens so skilfully set up by M. de Pauw represent two distinct species. The larger one, Iguanodon Bernissartensis, cannot be less than fifteen feet high, and, measured from the tip of the snout to the end of the tail, is rather over thirty feet long, covering nearly twenty-four feet of ground in its erect position (see Fig. 21). Iguanodon Mantelli is smaller and more slender looking, with a height of over ten feet, and a length of about twenty feet. (See Fig. 22.) [Illustration: Fig. 21.--Skeleton of _Iguanodon Bernissartensis_.] [Illustration: Plate VIII. IGUANODON MANTELLI. Length about 20 feet.] [Illustration: Fig. 22.--Skull and skeleton of _Iguanodon Mantelli_. (From Bernissart.)] The huge three-toed impressions found in Sussex prove that the monster, although owning a body as large as that of an elephant, habitually walked on its hind legs! Some of the thighbones found by Dr. Mantell measured between four and five feet in length. It will be seen that the fore limbs are small in comparison to the hind limbs. A remarkable feature of the hand is the large pointed bone at the end of the thumb, forming a kind of spur. The conical shape of this bone found by Dr. Mantell, who had no clue to its place in the skeleton, led him to suppose that it was a horn answering to that of a rhinoceros--a conclusion which Professor Owen refused for various reasons to accept. The latter concluded that it belonged to the hand, and now we see that he was right. Unfortunately, certain popular works on geology, such as _Our Earth and its Story_ (Cassell) still continue to spread this error, by showing a (very indifferent) restoration of the Iguanodon with the impossible horn on its nose. It has been suggested that the spur was a weapon of offence, and that, when attacked, an Iguanodon may have seized its aggressor in its short arms, and made use of the spur as a dagger. But this is only conjecture, and perhaps the spur may have been useful in seizing and pulling down the foliage and branches of trees, or in grubbing them up by the roots. Detached specimens of this curious bone may be seen among the other remains of Iguanodon at South Kensington, and also some of the gigantic tracks already alluded to. (Gallery IV. on plan, Wall-cases 5 and 6; and Gallery XI., Wall-case 7.)