284 MR. W. K. PARKER ON THE OSTEOLOGY OF BALAINICEPS REX. 
ting with the base of the petrosals, and its narrow terminal portion being exactly adapted 
to the basi-occipital. 
We now return to the structure of the basi-sphenoid in the adult bird. 
The structure of the basi-sphenoid of the Adjutant is less elegant indeed, but much 
resembles that of the Baleniceps; but its rostral portion is more like that of the latter 
than is the same part in the Heron. In this latter bird, at the point where the wing- 
like ecto-pterapophyses meet, in front of the aperture of the Eustachian tubes, the 
base of the skull becomes rather sharply carinate, and just in front of these coalesced 
ridges about one-fifth of an inch of the rostrum becomes synovial, the articular cartilage 
rising on each side of the mesial line about the twentieth of an inch. In the Boat-bill 
the rostrum is less carinate than in the Heron, and for four lines in extent the rostrum 
is coated with articular cartilage. We shall now show how the palato-maxillary fittings 
are attached to the rostrum in different birds; and these modifications may be con- 
veniently thrown into groups, the characters of which will sometimes have considerable 
family or relational value; whilst we shall often find that the same teleological modi- 
fications will occur in the most dissociated tribes. 
Modifications of the Basi-sphenoid in Relation to the Pterygo-palatine Apparatus. 
Group 1.—The ethmoido-frontals (the so-called ‘ nasals’’) and nasal processes of the 
pre-maxillaries being confluent with the principal or sphenoido-frontal, and the palatines 
having coalesced with each other and with the vomer, the carinate basi-sphenoid has no 
synovial cartilage. Motion is here limited to the pterygo-palatal and pterygo-quadrate 
articulations, ‘The vomer is arrested. 
Example :—Buceros, various species (the Hornbills). 
Group 2.—In this group there is a strong transverse synovial hinge, formed by the 
contiguous margins of the coalesced lacrymals and sphenoido-frontals posteriorly, and 
of the ‘nasals or ethmoido-frontals’ and nasal processes of the pre-maxillaries an- 
teriorly, which hinge is further strengthened by the procelian articulation of the ethmoid 
with the pre-sphenoid. The motion of this cranio-facial hinge is very free, the pterygo- 
palatal joints gliding along a considerable tract of the rostrum ; this process is adapted 
to them by being round, polished, and well covered with synovial cartilage. Answering 
to this structure, the pterygoids are long and slender, the quadrate bones and palatines 
high, or deep, and the vomer arrested. 
Example :—Psittacide (the Parrot-tribe). 
N.B. The Ramphastide or Toucan-tribe seem to connect this group with the next. 
‘ We have not the least doubt of the homology of these bones; they are evidently the representatives of 
the ‘nasals’ of the Mammalia; the ‘sphenoido-frontals’ of Professor Goodsir being simply the counterparts of 
the mammalian ‘ frontals.’ 
