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Show 1899.] OSTEOLOGY OF THE PYGOPODES. 1039 The Tubinares and Alcidae both develop large cnemial processes, which, as in the Pygopodes, project vertically beyond the femoral articular surface. But these never attain the size of those of the Pygopodes, and differ, moreover, in form. In the Alcidae the ento- and ectocnemial crests bear about equal shares in the formation of the process, but the former starts suddenly from the shaft just below the head of the tibia, in the Pygopodes it arises near the middle of the shaft and more or less gradually increases in size, and in the Tubinares it arises as in Alcidae, but immediately expands into a more or less flabelliforra plate. Outer aspect of the pelvic limb of Podicipes cristatus, nestling. p.t., proximal tarsal mass; other letters as in figs. 1 & 2. About the exact homology of the great cnemial crest of the Pygopodes there seems to be some doubt, even now. According to Shufeldt (18) it is to be regarded as representing the olecranon of the ulna, and both are to be treated " as mere extensions of the shaft of the bones " to w*hich they belong. The cnemial crest, or " rotular process," is stated by him to have a separate centre of ossification, separate from that of the tibial epiphysis. The patella, which has been held by 67* |