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Show 226 DR. R. W . SHUFELDT O N [Apr.], the hone, as in the case of the coracoid, being transversely flattened. Its antero-ventral end fuses with the coracoid, while its postero-ventral end goes to help form the dorso-superior part of the glenoid cavity. Its antero-superior angle articulates with the outer end of the corresponding clavicle, and its dorsal border articulates, for its entire length, with the superimposed suprascapula. The expanded dorsal part of the scapula is harmoniously extended by the still more dilated semi-osseous suprascapula. The dorsal border of this element of the girdle is markedly convex, the midpoint of its arc almost reaching to the transverse processes of the vertebras of the spine above it. In situ, it is seen to be a thin plate resting upon the last four cervical ribs by its mesial flat surface, being connected with the rest of the girdle in the manner we have described. The Interclavicle (episternum) is represented by an azygos bony bar, which is somewhat dilated and vertically compressed behind, while it is small and tapering in front, at which latter point it stands between the mesial ends of the clavicles, being slightly dorsad to them. Posteriorly its dilated extremity is attached to the ventral surface of the antero-mesial angle of the sternum, the union being through the medium of firm ligament. Either clavicle is represented by a slender, subcompressed bone articulating in a manner already indicated above. W h e n seen in situ it at first passes from its articulation with the interclavicle outwards. Near the middle point of its shaft it bends at a gentle angle upwards, and from thence goes to its facet, found at the autero-dorsal angle of the corresponding scapula. The mesial end of the clavicle is but slightly larger than its outer extremity, and the form of the bone thus affords a good classificatory character. Upon close examination, in some specimens, it m a y be discovered that its extreme outer tip may come into contact with the suprascapula at its antero-ventral angle. The Pectoral Limb.-Averaging some 3"4 centimetres in length, the humerus presents a rather short subcylindrical shaft, with scarcely any curvature. Its extremities are markedly expanded, the imaginary planes in which they lie intersecting each other at an angle of about 35 degrees. The head of the humerus is an elongated facet, and throughout life the sutural trace showing where this is united with the rest of the bone is distinctly visible. To the radial side of this is a bony crest for muscular insertion, having a form much as we see it in ordinary existing birds. This crest is turned ulnad so as to make an angle with the rest of the head of the bone, which is also similar to what we find in this last-mentioned class. Distally, there is an ulnar and radial tubercle, condylar surfaces for articulation with the bones of the antebrachium. In their form these also remind us of the corresponding structures in birds, though here in this Lizard the epiphysial sutural trace is visible during the life of the individual. The epiphysis in question includes the entire articular portion. Above the radial tubercle, the side of the expanded end of the shaft develops a moderately prominent ridge several |
