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Show 1895.] PRILLED LIZARD OP TROPICAL AUSTRALIA. 713 This takes the form of a voluminous denticulated frill, which the creature possesses the power of erecting and depressing at will. In adult individuals, the frill, when fully extended, may measure as much as eight or nine inches in diameter, and diverges at right angles to the long axis of the head. W h e n depressed the structure is relatively inconspicuous, being folded in symmetrical pleats around the creature's neck (see fig. 2, p. 717). The possession of living examples of Chlamydosaurus, both iu Queensland and, more recently, in Western Australia, has yielded m e the opportunity of observing and placing on record certain phenomena associated with its habits that are scarcely less remarkable than its structural peculiarities. Having, moreover, succeeded in bringing one of these singular Lizards alive to England, I had much pleasure in presenting the specimen to this Society's Gardens, where others specially interested in this animal group have been afforded opportunities of verifying the observations embodied in this communication. Iu the first place, with reference to the elevation and depression of the membranous frill, Chlamydosaurus is not unfrequently delineated in natural-history works with this structure more or less fully extended, but with the mouth completely closed. I have also observed mounted specimens in museums displaying a corresponding relationship of the organ and structure indicated. As a matter of fact, the opening of the mouth and the erection of the frill are synchronous actions which cannot be exercised independently of one another. A n explanation of this circumstance is afforded by the presence of slender processes of the hyoid bone which extend on either side through the walls of the membranous frill. The relative elevation of the frill is consequently in a direct proportion with the depression of the mandible, and it is only under the condition of the mouth being opened to its widest extent that the frill is so conspicuously displayed as to stand out at a right angle from the animal's neck, as illustrated in the drawing n o w exhibited (Plate X L L ) With regard to the significance and utility of the erectile frill in Chlamydosaurus, the fact that this structure is of insignificant proportions in young examples, and attains its full development only in adult individuals, would appear to indicate that, as a structure, it has been developed within comparatively recent times and does not represent the residual heritage of a remote ancestry. Respecting its function, there can, I think, be but little doubt that it fulfils simply the role of a " scare-organ," wherewith, being suddenly erected, it terrifies, and diverts the projected attack of, many ordinary enemies. The erection of the feathers of an owl or the fur of a cat is associated with a like function, but the inflation of the hood of the Cobra, and in a less degree the neck-membranes of other snakes, furnishes, perhaps, a more appropriate analogy. In one other Australian species, Amphibolurus barbatus, commonly known as the J ew Lizard, the throat membrane is also inflated under the influence of irritation in such a manner as to |