514 PKOCEEWNGS OF THE GEOLOGICAL SOCIETS". [June 25, 



at the fractured end 7g 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 Odontopteryoc could not have been less than between 

 5 and 6 inches (see 'restoration' proposed in PI. XVI. figs. 7 & 8). 

 There is no trace of external nostril in the preserved extent (1 inch) 

 of the upper beak-bone; a notch (PI. XVI. fig. 2, «) 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 (PI. 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 2\ lines (0-004| m.) ; 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 longi- 

 tudinal 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 tbe right side (PI. XVI. figs. 1 & 3, 2s) : it is 9| lines in 

 length (0-020 m.), 3 lines (0-006 m.) in least breadth, 7§ lines 

 (0-015 m.) in greatest breadth at the lower articular end, including 

 the zygomatic cup (ib. a). Of the two condyles there, the outer one 

 (fig. 3, 28 ») is a transversely extended convexity, the inner one 

 (ib. fc) is a narrower ridge-like convexity directed obliquely from 

 behind inward and forward, where it slightly expands ; a trans- 

 versely 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. 1,1). 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. 



