PROFESSOR OWEN ON THE GENUS DINORNIS. 135 
ridge (fig. 3,7) are approximate; both the mid vertical and transverse ridges of the 
superoccipital are less strongly marked than in D. crassus, D. elephantopus, and D. ro- 
bustus. With other smaller kinds of Moa, D. rheides exemplifies the less-mature age of 
the larger kinds in the minor indications of muscular force. The paroccipital part of 
the occipital surface bulges rather more abruptly outward and backward than in the 
larger crania above described, leaving a correspondingly deeper depression between that 
part (Pl. XII. figs. 2, 3, & 4,4) and the superoccipital tract (ib. 3). The masto-parocci- 
pital wall of the tympanic chamber (ib. figs. I & 4, 4,8) has a less angular, more arched, 
border than in D. erassus. The basioccipital mammilloid tuberosities (Pl. XII. figs. 2 
& 4, 11’) are less prominent. The posterior walls of the Eustachian canals (fig. 4, ¢) in 
one skull of Dinornis rheides are continuous, appearing to define the basioccipital from 
the basisphenoid, with a median emargination; but this is less marked in the two other 
crania of the same species. All show, more or less strongly, the remnant of the basi- 
sphenoidal mid vertical canal between the bases of the pterapophyses (5). 
The alisphenoid (fig. 4,6) swells out into an oblong tuberosity below the “ oval 
hole”; a deep notch, with a small venous perforation, divides the swelling from the 
pterapophyses (5’). The tuberosities are more prominent in Dinornis rheides than in 
D. elephantopus or D. crassus'; they correspond with the mesencephalic fosse, but are 
pneumatic, and due exclusively to the outer table and subjacent diploé. 
The orbitosphenoids (ib. 10) are as unmistakably indicated (in birds) by their 
essential characters as transmitters of the optic nerves, as are the alisphenoids by the 
oval foramina; no separate ossification of the descending orbital plate of the frontal 
in a young Grouse, or Goose, or other bird could be mistaken for an orbitosphenoid 
by any anatomist, save one constitutionally incompetent to appreciate or comprehend 
the grounds upon which true homology is determinable. 
The presphenoid (fig. 4,9) rostral in shape, as in all birds and most mammals, is of 
great length, as in other Dinornithes and the Struthionide generally ; it is compressed 
behind its mid part, and again expands to a breadth equalling that of its hind part in 
D. rheides: the under surface is subcarinate where compressed, transversely convex 
where expanded ; it terminates as usual, in a point. At its base it is confluent, above, 
with the orbito-sphenoids, and in advance of these with the prefrontals; the line of 
confluence with the latter extends outward in the form of a shelf, or transversely hori- 
zontal plate, with an obtuse terminal angle on each side (9”); on this plate rests the 
olfactory hoop (cingulum olfactorium). 
The prefrontals retain the characters of those in the previously described species, 
making no show (as they do in Struthionide”) upon the upper surface of the cranium. 
The confluence of the nasals with the frontals, prefrontals, and lachrymals is very com- 
plete; the cleft between the nasals (fig. 3, 15) persists anteriorly. 
* They are still more prominent in D. gravis, to be afterwards described. 
* Trans. Zool. Soe. vol. iii. pl. 39. fig. 1, 11 (Dromaius). 
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