PROFESSOR OWEN ON CNEMIORNIS. 257 
The greatest breadth of the cranial cavity is at the lateral depressions for the optic 
lobes, where it is 1} inch across; the greatest vertical diameter is 1} inch; the length 
of the cavity is 1 inch 9 lines; it is short, therefore, in proportion to its breadth and 
height. In the proportion of the mandibular to the cranial part of the skull, Cnemi- 
ornis, a8 is Shown in Pl. XXXYV. fig. 1, most nearly resembles Cereopsis (ib. fig. 6) 
among Lamellirostrals. 
There are no sutural indications of the limits of the parietals. The occipital 
surface, which, from its upper slope, appears in the view of the skull given in 
Pl. XXXV. fig. 3, through its more vertical position in Cereopsis does not there appear 
(ib. fig. 8); but a parietal tract (ib. ib. 7) is indicated in Cereopsis by the more marked 
and definite rise of the “frontal” covering (ib. ib. 11, 11) of the cerebral hemispheres. 
This difference is shown also in the profile views (fig. 1, 3-7, Cnemiornis; and fig. 6, 3-7, 
Cereopsis),in Pl. XXXY. 
The “ crotaphyte surface” (ib. fig. 6, ¢) is small and feebly indicated in Cereopsis ; 
the postcrotaphite surface (ib. pc) is better marked. In Cnemiornis both crotaphite 
(ib. fig. 1, #) and postcrotaphite (ib. pe) surfaces are better defined by intermuscular 
ridges. 
The “processes” of the mastoid are limited to that (8') which passes behind the 
joint for the tympanic to coalesce with the basisphenoidal extension (5') in Cnemiornis, 
as in Cereopsis and Aptornis; but in Aptornis there is a second, longer and stronger 
process of the mastoid, which descends external and anterior to the tympanic articu- 
lation *. 
The postfrontal is a long and strong trihedral process, terminating obtusely in 
Cnemiornis (Pl. XXXYV. fig. 1, 12), but extending forward to coalesce with the back- 
wardly produced lacrymal in Cereopsis, in which anserine the bony rim of the orbit 
is thus completed (ib. fig. 6, 73-12). 
The lacrymal is long, and directed backward as well as downward, in Cnemiornis (ib. 
fig. 1, 73), but terminates half an inch from the end of the postfrontal, leaving the 
lower part of the rim of the orbit incomplete to that extent. The hind part of the base 
of the postfrontal is deeply impressed by an oblong fossa (ib. fig. 4,1 ) in Cnemiornis ; and 
this fossa is well defined, though less deep, in Cereopsis. 
The upper part of the orbital rim, or frame, is more complete, better defined, in 
Cnemiornis, and is separated by a smooth upper tract of about 2 lines from the depres- 
sions for the superorbital mucous glands (ib. fig. 3, m m), which depressions are 
absolutely as well as relatively larger in Cereopsis, and cause by their pressure, combined 
with that of the eyeball from below, absorption of parts of the upper orbital border. 
The interspace between the glandular fosse is gently concave across, but undulated by 
a feeble mesial rising of the frontal. 
1 Tt is referred to in Dr. Hector’s Paper as the “‘ premastoid arch ;” but the process effects no junction with 
any outstanding part of the basis cranii. 
