BIRD. 99 in proportion to the face, than in any reptilia" except pterodactyls. The jaws are much elongat- ed, so as to form the hill, the outward shape of which, however, formed by the horny sheath, may be very different from that of its bony supports, in adaptation to habits of use. The upper mandible is formed anteriorly and mainly of the pnemaxilhe, and posteriorly by the paired niaxillaries and other bones, varying greatly in relative position and importance, and in many Idrds movable, so that the upper jaw is capable of a certain amount of up and down motion as on a hinge. These and other elements form a palate, the varying bony arrangement of which has been used with disputed success as a basis for general classification in ornithology. The lower jaw is formed of several elements now fused solidly together; and it is connected with the skull by the quadrates and other lesser bones and by a series of elastic cartilages permitting e.^treme movability and large expansion of the gape. rr f: OS ' , BIRD. rests the head of the femur. When one con- siders hoAV far beliind the centre of gravity of a bird's body the hip-joint is placed, and how it must sustain the whole weight of the body under BOXES or THE SKri.L OF A FOWI,. 1. Side View. 2. Lower Surface aud Palate (the lower jaw having bt^n removed): 3. Rear, or occipital, aspect. .So, Kupra-occipital ; Sii, K(]uaTnotiaI: Oc, occipital cond.vle: /", parietal: P/; posttrontal; F, frontal: O.S'. orblto-sphenoid; /. inter-orbital septum; Kth. ethmoid; /..lacrimal: .V. na- eal; I', Vom, vomer; mx. maxilla; Pm-v. preinaxilla; O/l optic foramen; Q, q, quadrate; Pg, ptg. pteryiroid; Pa, pal. palatine; /(, rostrum; J. ju*r. juRal; (^j, ((j'.quadrato-jugal; Eo, es-occipital (lateral occipital); 7')', t.vmpanic cavity; BO, ba«i-<i<-cij*ital; P.m.p.. poHt*?rior mandibular proccHs; J.w.fj., internal articular process; Alt, articular; A, aniiular; .S.4. supra-auKular; U. dentary; C, choana (one of {he pilr of inner narial openings); BT, basi-temporal; fb. foramina for cerebral nerves. Legs. — The limbs of birds conform to the ver- tebrate type, with certain modifications, which are least in the hinder pair. They are attached to the 'pelvic arch,' which in birds consists of some solidified sacral and coccygeal vertebrie and the paired pelvic bones (ilium, ischium, and os pubis), which latter meet to form a cup in which TARSAL E.N'TELQPES. 1. Booted. 2. Scutellate. 3. Reticulate. 4. Reticulate-scutellate. unfavorable circumstances, as well as provide for the leverage of the muscles of the thigh, the necessity for this consolidation, breadth, and mas- siveness will be perceived. The thigh is short, and concealed within the body; the next division, often mistaken for the thigh, is the leg. strictly so called, or tibia and fibula, which ends at what is really the ankle-joint, although popularly re- gardeu as the knee: and beneath this is the shank, commonly called the fa r.sws, which in some birds is very long, serving as a part not of the foot, but of the leg, and formed by a compound bone, composed of the united metatarsal bones, with the upper end of which four tarsal bones are fused. Thus the ankle-joint is not between the tarsus and metatarsus, but between two series of tarsal bones. The tibia is therefore jiroperly a tibiotarsus. and the so-called tarsus is really a tarsometatarsus. The feet are di- vided into toes, which are four in number, three before and one behind, difl'ering from each other in length and in the number of jointsorphalanges of which they are composed, the hallux, which is directed backward, being in general compara- tively short, and consisting of two joints only. Xo tifth toe is kno«Ti, and the hallux (first toe) is absent in the Struthiones. which have lost also the second, while the fourth is diminished, throwing the work almost alone ujion the third, or middle toe. Wings and Shoulder-Girdle. — The anterior limbs or wings of a bird are the fore limbs of other vertebrates modified for the purposes of flight. They are attached to the shoulder-girdle or pectoral arch of the skeleton, which in this, class is of extraordinary strength and impor- tance. It consists of the thoracic case formed by the dorsal vertebra", the true ribs and the breast-bones (sternum), which are connected by ligaments and ossifications. All the bones of birds are dense and hard. The sternum is re- markably large and strong, serving for the at- tachment of the muscles which depress the wings. It generally exhibits a projecting ridge, or keel, along the middle, which is proportionately largest in birds of most powerful tlight or swim- ming ability, and is wanting only in the liightless- birds (see above). This plate ossifies only as- the bird niatuies, being in early life a cartilage, the flexibility of which may easily be felt in young fowls, affording housekeepers a test for alleged'spring'cliickens. The variations in form of the sternuiii are of considerable taxonomic significance. Outside and attached to this case
