at the fractured end 712 lines (0⋅017 m.); the transverse diameter of the base, at the parallel of the fronto-nasal suture and at the alveolar borders, is 1 inch (0⋅025 m.), at the fractured end 9 lines (0⋅018 m.).
From the gradual loss of dimensions in the basal extent of the bony upper mandible here preserved, I estimate that the length of the beak from the fronto-nasal suture must have exceeded that (2 inches 5 lines) of the skull behind such suture, and that the total length of skull of Odontopteryx could not have been less than between 5 and 6 inches (see 'restoration' proposed in Pl. XVI. figs. 7 & 8). There is no trace of external nostril in the preserved extent (1 inch) of the upper beak-bone; a notch (Pl. XVI. fig. 2, n) at the fractured fore border, left side, may be part of such; but it is narrow, and is like a similar notch and obvious fracture situated further back, on the right side of the fossil. The malar zygoma (Pl. XVI. figs. 1, 2, 4, 26) is continued from the sublacrymal part (fig. 2, 73) of the base of the beak above the longitudinal lateral groove; below that groove the upper jaw appears to have terminated behind in a short free point (fig. 2, 21); but such, if it existed, bas been broken away on both sides. The groove reappears on the zygoma, and indents the middle of its outer surface; the least vertical diameter, beneath the middle of the orbit, of the zygoma, is 212 lines (0⋅00412m.); toward the fore part of the orbit this diameter gradually augments; but the bone is broken away at the junction with the lacrymal, together with the lower part of that bone (fig. 2, 73); its conjunction and seeming continuation with the base of the upper beak-bone, above the longitudinal groove, is preserved. Prom this part, on the parallel of the fronto-nasal suture, an extent of 1 inch 5 lines (0⋅036 m.) of the left zygoma is preserved, and nearly as much of the right zygoma; both appendages diverge with a slight downward slope toward the zygomatic cup (h) at the outer border of the tympanic (28) above its mandibular condyles.
The tympanic is preserved in its natural articulation with the mastoid on the right side (Pl. XVI. figs. 1 & 3, 28): it is 912 lines in length (0⋅020 m.), 3 lines (0.006 m.) in least breadth, 712 lines (0⋅015 m.) in greatest breadth at the lower articular end, including the zygomatic cup (ib. h). Of the two condyles there, the outer one (fig. 3, 28 i) is a transversely extended convexity, the inner one (ib. k) is a narrower ridge-like convexity directed obliquely from behind inward and forward, where it slightly expands; a transversely concave groove or channel, in a similar oblique course, divides the condyles. A groove of a line breadth divides the outer condyle from the zygomatic (tympano-squamosal) cup (ib. h). The shaft of the tympanic is triedral, with one margin slightly rounded, turned outward, another inward or mesiad (fig. 3 28), and with the anterior and internal sides converging upon, and extended into, the orbital process (fig. 1, l). The zygomatic cup is supported on a very short prominence, not produced forward so as to augment the fore and aft diameter of the distal end of the bone, which diameter is uniform and short in comparison with the transverse.
