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PACHYORNISLYDEKKER.
The skull is either vaulted or flattened, with a sharp and narrow beak. The paroccipital processes are shorter and more rounded, and the basi-occipital tubercles more prominent than in Anomalopteryx, while the quadrate and mandible resemble the same bones in that genus somewhat closely. The sternum is flat and very broad and short, with no coracoidal facets, a very small xiphisternal notch, broad and short costal processes, and widely divergent lateral processes; while there are only two costal articulations. The pelvis is extremely low and wide, with the anterior wall of the acetabulum very deeply concave, the ventral surface of all the vertebrae behind the true sacrals narrow and convex, and from which the very broad sacral ribs ascend to join the ilium, of which the inferior postacetabular border is very sharp, and descends far below the level of the ribs. There is no pectineal process to the pubis. The tibio-tarsus is very short, with the shaft curved outwards, the distal extremity markedly inflected, and the fibular ridge much shorter than in the other genera. The fibular border below the smooth space at the distal extremity of the fibular ridge is extremely rough; and the distal extensor tubercle is very prominent, being situated partly on the line of the upper half of the extensor groove, instead of being altogether external to the same.
The tarso-metatarsus is still shorter and wider than in Emeus, the width at the middle of the shaft being usually rather more than one third of the length. The third trochlea is more prominent than in the other genera, and rises very abruptly from the shaft, the outer border of the anterior surface usually expanding suddenly at the proximal extremity, and the outer ridge of this surface being always more prominent than the inner, whereas in the other genera the opposite condition obtains. The femur, as compared with that of Dinornis, is very much shorter and thicker, with a longer neck, and the head rising and projecting very considerably, the linea aspera mainly forming a rough nodule near the distal end of the shaft, the outer surface of the distal extremity more suddenly expanded, and the popliteal depression larger, more open, and leading to the inner surface of the shaft by a more distinct channel. The profile of the inner condyle is wider antero-posteriorly, and more rounded, the anterior intertrochlear surface being deeply channelled.
The phalangeals of the pes are much shorter and stouter than in Dinornis, the proximal surface of the terminal segments generally presenting a trefoil-shaped contour. The length of the tarso-metatarsus is very much
