Mammalia, and is provided with a gall-bladder. In the presence of three distinct bones developed from cartilage in the shoulder-girdle (viz. scapula, coracoid, and pre- or epi-coracoid) the Monotremes agree with the Anomodont reptiles (see p. 83), and with no other representatives of that class. The pre-coracoid of the Anomodonts is, however, distinguished by extending upwards to articulate with the acromial process of the scapula. The Monotreme humerus is, moreover, strikingly like the corresponding bone of many of the Anomodonts and of some of the allied Labyrinthodont Amphibians. _Family_ ORNITHORHYNCHIDÆ. _Ornithorhynchus._[32]—Cerebral hemispheres smooth. Premaxillæ and mandible expanded anteriorly and supporting a horny beak something like that of a duck, bordered by a naked and very sensitive membranous expansion. The place of teeth in the adult is supplied functionally by horny structures, elongated, narrow, and sharp-edged, along the anterior part of the sides of the mouth, and broad, flat-topped or molariform behind. Functional molar teeth present in the young and adolescent condition. Legs short, fitted for swimming; feet webbed, each with five well-developed toes armed with large claws, beyond which in the fore feet the interdigital membrane is extended. Vertebræ: C 7, D 17, L 2, S 2, Ca 21. Acetabulum not perforated. Tongue not extensile. Mucous membrane of small intestine covered with delicate, close-set transverse folds or ridges. Tail rather short, broad, and depressed. Eyes very small. Fur close and soft.