OCR Text |
Show 110 MR. C. W. ANDREWS ON REMAINS OP ^EPYORNIS [Feb. 6, 1 cm., but the summit is broken away. This projection occupies just the position of attachment of the hallux in such birds as possess one, and it may represent the ligament by which the hind toe was attached ossified from age. The trochleas are large and are arranged along a slightly curved line. The middle one is broadest and projects beyond the others; its sides are deeply concave and its articular groove only very slightly oblique to the long axis of the bone. Of the other two, the inner is the smaller, but projects slightly beyond the outer. There are no projections at the lower end of the channel for the tendon of the adductor of the outer digit, such as are figured in the tarso-metatarsus of AS. hildebrandti. In both the present specimen and in that described by Burckhardt (2) the width of the distal end is greater, in proportion to the least circumference of the shaft, than it is in the tarso-metatarsi from the coast. The tibio-tarsus is complete except the postcondylar processes, which are broken away. The bone on the whole resembles that of AS. hildebrandti, but differs from it in size and in some other respects. The dimensions are:- Length Width of distal end Width of shaft at narrowest point Circumference of shaft at the same point M., sp. cm. 57-5 10-0 5-0 14-0 M. maximus. M. hildebrandti, cm. 64-0 135 155 cm. 48-0 8-2 11-0 It will be seen from the above table that the tibio-tarsus, hke the tarso-metatarsus, is intermediate in size between the corresponding bones of AS. maximus and AS. hildebrandti, and it is also rather longer in proportion to the tarso-metatarsus than is the case in AS. hildebrandti. The antero-posterior flattening and the curvature of the shaft, which are characteristic of the genus, are well marked. The distal articulation fits exactly into the proximal one of the tarso-metatarsus above described, and there is no doubt that the two bones belong to the same species, if not to the same individual. The median ridge between the condyles figured in the tibio-tarsus of AS. hildebrandti (2) is here wanting. The cnemial crest is moderately developed and rises a little above the proximal articular surface. On the upper outer surface of the ectocnemial crest is a foramen, probably pneumatic, the exact size of which cannot be determined, its edges being broken away owing to the thinness of the bone at that point. |