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NOTE ON THE SO-CALLED SECOND BEANCHIAL AECH IN 
LIZAEDS. 
By John Hewitt. 
(With one Text-figure.) 
The occurrence of an isolated cartilaginous element, apparently a 
branchial arch, in the neck of certain adult lizards was emphasised by Mr. 
F. E. Beddard in a paper ''On the Anatomy of Certain Species of Squamata'" 
('Proc. Zool. Soc.,' 1907, p. 53). This element had been previously observed 
by Prof. W. K. Parker in the adult skull of Lacerta agilis, but, perhaps 
owing to a somewhat ambiguous description ('Phil. Trans.,' 1879, p. 616), 
the fact has been generally overlooked by the writers of text-books on 
vertebrate Zoology ; there is, however, a clear account of the hyoid and bran- 
chial apparatus in T. J. Parker's chapter on the Lizard in his ' Zootomy,' 
p. 146. 
It is commonly stated that, whereas the hyoid apparatus both of Chelonia 
and of Lacertilia is provided with two pairs of large horns, those of Chelonia 
belong to the first and second branchial arches, the hyoid arch being repre- 
sented only by a small or obsolete horn, whilst in Lacertilia the two horns 
belong to the Hyoid and first branchial arches. As a matter of fact, the 
hyoidean apparatus of lizards (see Hoffmann in Bronn's ' Tierreich,' " Eep- 
tilien," p. 608, Taf. 72; Beddard in 'P. Z. S.,' 1905, p. 20; Shufeldt in 'P. Z. S.,' 
1890, p. 224, PI. 18) varies considerably, the two horns showing various 
degrees of development, whilst there may or may not be present a posterior 
bifurcation of the median piece which very probably is a persistent remnant 
of the second branchial arch, as thus considered by T. J. Parker. When 
present, this pair of basibranchial processes may be closely approximated in 
the middle line, or they may be widely separated as in P achy dacty his hihroni 
and some other geckoes ,- in closely allied genera they may be strongly 
developed or completely absent. The one character, which may point to the 
lack of true serial homology between these basibranchial processes and the 
two pairs of cornua, is the absence of any joint to mark them off from the 
median copula, whereas the cornua appear to be almost always articulated 
therewith. However, the presence of joints in the hyoidean apparatus seems 
to be sometimes merely a matter of function. At the anterior bend of the 
hyoid arch of lizards, the element is more or less completely divided into two, 
a dorsal and a ventral half, being completely so in Varanus, whilst, on the 
other hand, in Gerrhosaurus validus I have found no trace of a joint or separa- 
tion into two halves. Again, in the Agamidae, as known to me in the genus 
Agama, the l)ase of the hyoid arch has almost entirely fused up with the 
