126 PROFESSOR OWEN ON THE GENUS DINORNIS. 
extends backward beneath the fore part of the cranial cavity as far as the back part of 
the orbits. ‘The outer layer of the prefrontal projects from beneath the angle between 
the nasal and frontal, or lachrymal, very much in the ordinary position of the external 
part of the prefrontal in Reptiles and Fishes. 
The nasals (ib. figs. 1, 3, 5,15) are confluent posteriorly with the frontals (ib. 11), 
below with the upper expanded plates of the prefrontals (ib. fig. 5, 14), externally with 
the lachrymals (ib. 73), and internally or mesially with each other as far as the prefrontal 
confluence, in advance of which their median suture persists. The maxillary process 
(ib. fig. 5, 15”) appears to be shorter, and the premaxillary part (ib. 15) longer and more 
pointed than in Dinornis robustus. The smooth shallow depression (ib. fig. 3, 15) on 
which the premaxillary glides is narrower than in D. robustus; the raised, usually 
rough, surface external thereto contracts in breadth to near the pointed fore end of the 
bone, the upper part of which is smooth. 
The cranium is longer in proportion to its breadth than in D. robustus. The occipital 
region is relatively of less extent vertically and transversely, and its middle part more 
completely overhangs the basioccipital condyle. ‘The transverse extent of the cranium 
between the descending antorbital processes is markedly inferior in D. elephantopus, the 
vertical extent at the mid line being somewhat greater than in D. robustus. 
The tympanic (ib. fig. 1, 28) differs from that of Dinornis robustus (Vol. V. pl. 53. 
fig. 2, 28) in the less-concaye upper border of the orbital process (4) and in the smaller 
cavity (h) for the squamosal. 
The posterior articular surface of the squamosal presents a convexity at the back part 
of the inner surface of the bone, fitting into the depression of the tympanic, and a con- 
cavity in advance adapted to the convexity on the tympanic process in front of the 
depression. The low obtuse ascending malar process to meet the postfrontal is better 
defined than in D. robustus. 
Perhaps the best and most recognizable distinction between Dinornis robustus and 
D. elephantopus is in the not only absolutely but relatively smaller size of the mandi- 
bular parts of both upper and lower jaws in the latter species. The beak was shorter, 
more slender, and less obtusely terminated. The premaxillary with the most entire 
nasal process in my present series gives a total length of 3 inches 3 lines (ib. fig. 1, 22, 22’); 
that process expands posteriorly to a breadth of 6 lines (ib. fig. 6); but in the largest 
skull (belonging to the skeleton described in vol. iv.) the nasal articular surface indi- 
cates a rather broader process. As it advances the nasal branch loses breadth as it 
gains in depth, and is impressed at its narrowest part by a longitudinal groove. The 
lateral margins, as the branch contracts, bend downward and inward and meet to form 
the prenarial septum (ib. fig. 1,s), from the free margin of which to the tip of the beak 
measures 1 inch 7 lines. 
The rough punctate surface sheathed by the horny bill passes rather gradually behind 
into the smooth septal plate. The maxillary branches (ib. figs. 1, 6, 22”) diverge back- - 
