252 Transactions of the Royal Society of South Africa. 
5. If (Q) is the quadrate, i.e. if Meckel's cartilage only secondarily 
comes to articulate with the adult quadrate, then the common view that 
the mandibular bar becomes bent in the form of a > to form the upper 
and lower jaws does not exactly express the facts of the case ; for on this 
view the palatine cartilage is the most dorsal portion, the quadrate the 
ventral portion, of the upper segment. If my view is the correct one, 
then the palatine, which is the original articulation for Meckel's cartilage, 
must be ventral to the quadrate. I am thus going against accepted ideas 
in accepting an original palatal and secondary quadrate articulation of 
Meckel's cartilage ; and these accepted ideas are so well supported by the 
structure of Selachii, Batoidei, and embryonic stages of higher groups 
that opposite views must be treated with caution. But if the "posterior 
lateral" cartilages of Petromyzon and the ''coronal" cartilages of Bdello- 
stoma should prove to be homologues of Meckel's cartilage, then my 
view would receive strong support, since these are admittedly most 
primitive groups. Also the structure of the jaws of the Holocephalan, 
Ghimaera (with anterior, i.e. palatal, articulation of Meckel's cartilage) 
supports my view that the formation of the jaws is not simply a bending 
of the mandibular arch in the form of a > ; that the posterior articulation 
of the lower jaw is secondary. 
Second Bar. — In the Xenopus tadpole there is no indication that the 
hyoid has any part in the formation of the stapedial portion of the 
columella auris. The two hyoid bars are joined to a basi-hyal (BH Fig. 7) 
which is continuous w^ith a basi- branchial (BB Fig. 7). At their outer 
edges the two hyoids are firmly attached by ligaments to the palatines at 
points (x Fig. 7) just posterior to the articulations of Meckel's cartilages. 
The outer edges of the hyoids are also joined by a stout plate of muscle 
fibres (Fig. 1 MH), and the contraction of these would cause the hyoid bars 
to bend upwards at their inner ends so that the mouth cavity would be 
reduced. If the mouth be filled with water, then closed and the " hyoid " 
muscle contracted the water would be forced through the pharynx ; the 
hyoid bar is thus probably important for the processes of nutrition and 
respiration. 
Branchial Bars. — The branchial skeleton consists of two plates joined 
to a median basi-branchial (BB). Each plate has four apertures, 
and the fact that there is an artery in connection with each of 
these may induce one to believe that there are really five branchial 
bars. Such an opinion would be strengthened by an inspection of the 
outline of the branchial plate which clearly shows five projections, 
a, h, c, d, and e, alternating with the apertures 1, 2, 3, and 4. Against 
the presence of five instead of four branchial bars, the following points 
may be raised : — 
1. There are only three internal pharyngeal grooves, the first one 
