ORNITHORHYNCHUS paradoxus, in natural history, a singular quadruped, re markable for its structure. The head is similar to that of a duck, which would lead to the supposition that it belonged to an aquatic bird. Both jaws are as broad and low as those in a duck, and the calvaria has no traces of a suture, as is generally the case in full-grown birds. In the cavity of the skull there is a consi derably bony falx, which is situated along the middle of the os frontis, and the ossa bregmatis. The mandible of this animal consists of a beak, the under part of which has its margin indented as in ducks, and of the proper instrument for chewing that is situated behind, within the cheeks. Dr. Shaw says it has no teeth, though Mr. Home found, in a specimen examined by him, two small and flat molar teeth on each side of the jaws. The forepart of this mandible, or beak, is covered and bordered with a coriaceous skin, in which three parts are to be distinguished, viz. the proper integument of the beak ; the labiated margins of it ; and a curious edge of the skin of the beak. Into these three parts of that membrane numerous nerves are distributed, intended, proba bly, as the organs of feeling, a sense which, besides men, few mammalia enjoy ; that is, few animals possess the faculty of dis tinguishing the form of external objects, and their qualities, by organs destined for that purpose, a property very differ ent from the common feeling, by which every animal is able to perceive the tem perature and presence of sensible ob jects, but without being informed, by the touch of them, of their peculiar qualities.
Thus the skin in the wings of the bat, and its ear, are supposed the organs of common feeling, by means of which they are enabled to flutter, after being blind ed, without flying against any thing. The whiskers of many animals appear likewise to serve the same purpose of informing them of the presence of sensible bodies, and hence they have been compared to the antenna of insects. But to return to the ornithorynchus : it is an animal which, from the similarity of its abode, and the manner of searching for food, agrees much with the duck, on which account it has been provided with an organ for touching, viz. with the integu ment of the beak richly endowed with nerves. This instance of analogy in the structure of a singular organ of sense in two species of animals, from classes quite different, is a most curious circum stance in comparative physiology, and hence the ornithorhynchus is looked up on as one of the most remarkable pheno mena of zoology. There are two species, both inhabitants of New-Holland. OROBANCHE, in botany, broom-rape, a genus of the Didynamia Angiospermia class and order. Natural order of Per sonatx. Pediculares, Jussieu. Essential character : calyx bifid ; corolla ringent ; capsule one-celled, two-valved, many seeded; gland under the base of the germ' There are fourteen species.