No reptile, therefore, would be covered with feathers, neither, judging from those we know to-day, would they be clad in fur or hair; but, such coverings being barred out, there remain a great variety of plates and scales to choose from. Folds and frills, crests and dewlaps, like beauty, are but skin deep, and, being thus superficial, ordinarily leave no trace of their former presence, and in respect to them the reconstructor must trust to his imagination, with the law of probabilities as a check rein to his fancy. This law would tell us that such ornaments must not be so placed as to be in the way, and that while there would be a possibility--one might even say probability--of the great, short-headed, iguana-like Dinosaurs having dewlaps, that there would be no great likelihood of their possessing ruffs such as that of the Australian Chlamydosaurus (mantled lizard) to flap about their ears. Even Stegosaurus, with his bizarre array of great plates and spines, kept them on his back, out of the way. Such festal ornamentation would, however, more likely be found in small, active creatures, the larger beasts contenting themselves with plates and folds. Spines and plates usually leave some trace of their existence, for they consist of a super-structure of skin or horn, built on a foundation of bone; and while even horn decomposes too quickly to "petrify," the bone will become fossilized and changed into enduring stone. But while this affords a pretty sure guide to the general shape of the investing horn, it does not give all the details, and there may have been ridges and furrows and sculpturing that we know not of. Knowing, then, what the probabilities are, we have some guide to the character of the covering that should be placed on an animal, and if we may not be sure as to what should be done, we may be pretty certain what should not. For example, to depict a Dinosaur with smooth, rubbery hide walking about on dry land would be to violate the probabilities, for only such exclusively aquatic creatures as the whales among mammals, and the salamanders among batrachians, are clothed in smooth, shiny skin. There might, however, be reason to suspect that a creature largely aquatic in its habits did occasionally venture on land, as, for instance, when vertebrae that seem illy adapted for carrying the weight of a land animal are found in company with huge limb-bones and massive feet we may feel reasonably certain that their owner passed at least a portion of his time on _terra firma_.