1907.] OF CERTAIN SPECIES OF SQUAMATA. 53 



as those of Hatchett Jackson *, Gaclow t, and Sedgwick J, which 

 may be regarded as expressing the current knowledge of the 

 subject. Nevertheless, the late Prof. W. K. Parker§, in describing 

 the adidt skull of Lacerta agilis, wrote as follows : — " Another bar, 

 half as long as the first, and unossified, lies behind the first 

 branchial above ; it is /-shaped, with the top hooked inwards, 

 like the lower piece ; this is the upper (6r.^), or ' epibranchial ' 

 part ; it has a small snag outside its middle. Besides this, there 

 is, on each side, a slender, slightly outbent hypo- branchial (Ji.hr. )\ 

 this belongs to the second branchial, and also from its length is 

 evidently part of the third, neither of which chondrify, above, in 

 the embryo." In a footnote is added the remark that "this little 

 highly-metamorphosed Lizard has scarcely thrown aside the 

 skeleton of these organs of aquatic respiration." It is obvious 

 that Prof. Parkei-'s account is a little misleading, and this doubt- 

 less accounts for the fact that the existence of remains of a second 

 branchial arch in Lacerta has been largely ignored in zoological 

 literature. What he speaks of as an " epibranchial," without 

 determining to which arch it belongs, but letters " &r.'V' is clearly 

 from its position a vestige of the second branchial arch, as is plainly 

 recognised in Prof. T. J. Parker's 'Zootomy' and in his 'Textbook 

 of Zoology,' written in conjunction with Prof. Haswell Ij. The 

 exceptional character of the hyoid complex of Lacerta in possess- 

 ing " the epibranchial of the second branchial arch " is properly 

 emphasised by Dr. Shufeldt % in reviewing existing knowledge of 

 the Lacertilian hyoid bones. 



The third postmandibular arch is, however, by no means a 

 peculiarity I'estricted to T^cCcerta. It occurs in Zonuriis in the 

 form of a short and slender bar lying behind the well-developed 

 first branchial bar**. This bar of cartilage does not extend down 

 to the median copula, and indeed falls a considerable distance 

 short of it. I have examined three other Lacertilians in which 

 this same visceral arch is represented and one in which it is not 

 to be found ; but I have not at present attempted an exhaustive 

 research into the facts of its absence or presence among the 

 different families of Lacertilia. I could not detect the bar of 

 cartilage in Ghamceleolis, whose anatomy has been described above. 

 It is well developed in both Tiliqua and Trachydosaurus. In the 

 former (text-fig. 15, p. 54) it is very conspicuous, and it is not a 

 little surprising that it has been missed, unless I have unwittingly 

 overlooked its description somewhere. But if this be the case it is 

 clear that its existence has escaped the writers of many textbooks. 



* 2nd ed. of Rolleston's ' Forms of Animal Life.' 

 t " Amphibia and Reptilia," in ' Cambridge Natural Historj'.' 

 j ' Textbook of Zoology,' vol. ii. 



§ " Development of Skull in Lacertilia," Phil. Trans. 1879, p. 616. 

 II 'Textbook of Zoologj-,' vol. ii. 

 Tf P.Z.S. 1890, p. 225. 



** There is no trace of this shown in a figure of the hyoid of Zoniirus cordylus 

 copied from Henle in Bronn's ' Thierreich,' Reptilien, vol. vi. Abth. iii. Taf. 107. 

 fig. 33. 



