MR. W. K. PARKER ON THE OSTEOLOGY OF BALAZNICEPS REX. 313 
leading to the rich diploé of the light, expanded, articular portions of the jaw. Several 
other pneumatic holes lie in the deep smooth concavity between the articular facets ; 
and there is here and there a larger passage of the same nature on the internal face of 
the broad part of the ramus. The posterior angle of the jaw is half an inch below and a 
little behind the external articular facet ; this angle is tubercular, and soon loses itself 
in the strong convex inferior margin of that flat, crescentic, smooth end of the mandible, 
the inner extremity of which has been described above. This broad end of the man- 
dible, which passes a little forwards as well as inwards, is 13 inch in extent; and here 
the two inner angular processes of the opposite rami are only two-thirds of an inch 
apart. The large vascular foramen (inferior dental) is within, and half an inch behind 
the highest coronoid part of the jaw; it has a tubercle for muscular attachment close 
above it, another behind, and another still larger on the external margin, one-third 
of an inch external to it. The smooth, rounded, narrow inferior edge of the hinder 
part of the mandible, at 1} inch from the end, swells out and rises gently, becoming 
again slightly carinate as it nears the external angular process. 
Subjoined is a Table of comparative measurements showing the length of the man- 
dible measured along the curve, and the extent of the coalesced symphysis, in different 
birds, in inches and lines (or twelfths of an inch) ; also their proportion to each other. 
Length of Mandible. Length of Symphysis. Proportion. 
in. lines. in, lines. 
Caprimulgus europeus . . 1 6 0 3 a 
Podargus humeralis . 2 8 0 ile st 
Cancroma cochlearia . 4 8 0 33 qi 
Baleniceps rex 8 6 1 2 + nearly. 
Ardea cinerea . 6 3 1 3 d 
Ciconia argala . 15 4 4 8 + nearly. 
Buceros bicornis . 11 8 7 8 2 
Macrocercus ararauna 2 6 1 1 2 
Calyptorhynchus naso 2 4 1 0 3 nearly. 
Diomedea exulans 9 6 OPO zy nearly. 
Platalea leucorodia . 8 0 2 8 3 
Pelecanus onocrotalus 17 9 0 3 a 
We see by the above table that the symphysis, in the Common Goatsucker, is twice 
as long, in proportion to the length of the jaw, as in the Pelican, and that the Boat-bill 
is four and a half times as strong at that part of the jaw, whilst the Baleniceps has 
just ten times as much symphysis as the Pelican. Buceros bicornis is quite without a ; 
peer in this part of its anatomy, although the Parrots come very near it. The relative 
length of the dentary portion of the mandible to the entire ramus is another very 
important point in the anatomy of the Bird’s head ; for, as a rule, the strong horny 
sheath reaches to the posterior end of this element of the mandible. 
In the next table the length of the mandible is put into parallelism with the extreme 
length of the dentary, which overlaps the articular moiety of the ramus at its posterior end. 
