With regard to the hair, the scales, the scutes, and other modifications of the skin, in some instances the analogy of the nearest allied living forms of animals has been the only guide; in a few instances, as in that of the Ichthyosaurus, portions of the petrified integument have been fortunately preserved, and have guided the artist most satisfactorily in the restoration of the skin and soft parts of the fins; in the case of other reptiles, the bony plates, spines, and scutes have been discovered in a fossil state, and have been scrupulously copied in the attempt to restore the peculiar tegumentary features of the extinct reptiles, as _e.g._ in the Hylæosaurus. In every stage of this difficult, and by some it may be thought, perhaps, too bold, attempt to reproduce and present to human gaze and contemplation the forms of animal life that have successively flourished during former geological phases of time, and have passed away long ages prior to the creation of man, the writer of the following brief notice of the nature and affinities of the animals so restored feels it a duty, as it is a high gratification to him, to testify to the intelligence, zeal, and peculiar artistic skill by which his ideas and suggestions have been realised and carried out by the talented director of the fossil department, Mr. Waterhouse Hawkins. Without the combination of science, art, and manual skill, happily combined in that gentleman, the present department of the Instructive Illustrations at the Crystal Palace could not have been realised. The Secondary Island. The most cursory observation of the surface of the earth shows that it is composed of distinct substances, such as clay, chalk, lias, limestone, coal, slate, sandstone, &c.; and a study of such substances, their relative position and contents, has led to the conviction that these external parts of the earth have acquired their present condition gradually, under a variety of circumstances, and at successive periods, during which many races of animated beings, distinct both from those of other periods and from those now living, have successively peopled the land and the waters; the remains of these creatures being found buried in many of the layers or masses of mineral substances, forming the crust of the earth. The object of the Islands in the Geological Lake is to demonstrate the order of succession, or superposition, of these layers or strata, and to exhibit, restored in form and bulk, as when they lived, the most remarkable and characteristic of the extinct animals and plants of each stratum. The series of mineral substances and strata represented in the smaller island have been called by geologists “secondary formations,” because they lie between an older series termed “primary,” and a newer series termed “tertiary:” the term “formation” meaning any assemblage of rocks or layers which have some character in common, whether of origin, age, or composition.[1]