DEVELOPMENT OF THE SKULL IN THE LACERTILIA. 
615 
(figs. 3, 4, 6). The bony bar ends in cartilage, the outer part of the stem (nearly 
half) is unossified, and there is a large trifoliate growth of cartilage abutting 
externally against the tympanic membrane (Plate 43, figs. 3, 4, 6 ; and Plate 45, fig. 6), 
The “ middle ear ” in this Lizard is typical of what is seen in all the Sauropsida 
above the Serpents; * and therefore is worthy to be worked out exhaustively, and 
described fully. 
The position of the columella, stretching from the fenestra ovalis to the membrana 
tympani, is seen also in Plate 43, fig. 4 ; in fig. 3, the extra- and infra-stapedial cartilages 
are seen from the outside ; the former is seen through the membrane, which is stretched 
upon the r im of the hollowed quadrate (q.), and the latter is seen to escape from the 
drum-cavity, as if it would unite with the stylo-hyal (Plate 45, fig. 6, i.st., st.h.), which 
it does in Hatteria (Huxley, op. cit., p. 397), and in the Bird. (See “Bird’s Skull,” 
Part II., Trans. Linn. Soc. (Zool.) vol. i., plate 20, fig. 7.) 
As in many Birds the supra-stapedial ( s.st .) is bilobate, the outer broad lobe being a 
continuation upwards of the tongue-shaped extra-stapeclial (e.st.) ; the inner lobe, the 
true supra-stapedial, as in Hatteria, and many of the Batrachia (e.g., liana pipiens) is 
united to the ear-capsule by cartilage. Here it is almost fibrous at the middle where 
it thins out. 
The “ stapedius ” muscle arises (fleshy) from the outer part of the paroccipital 
process (opisthotic and exoccipital combined), and is inserted (fleshy) between the 
outer broad, and the inner narrow, lobes of the supra-stapedial (Plate 43, figs. 4, 6, 
st.m.). 
In this section the facial nerve (VII) is seen passing out over the columella; the 
fenestra rotunda leading to the rudimentary cochlea is seen in the side and end views 
(Plate 43, figs. 4 and 8 ,fr.). 
Here, as in the Tortoise and Crocodile, the os quadratum is hollowed out to form the 
ear-drum; in the Bird that bone is pneumatic, and opens into the drum, but the main 
part of the cavity is formed by a hollow shell-like wing of the exoccipital (par- 
occipital), the floor being formed by the basitemporal, and the roof by the tegmen 
tympani and squamosal; in many Birds there is a chain of tympanic bones that serve 
to strengthen the ring of the parchment: these parts are attached to the quadrate in 
some degree. 
The endoskeletal part of the mandible, e.g., quadratum, articulare, and Meckel’s car¬ 
tilage, have already been partly described ; the quadrate is seen in the side view 
(Plate 42, fig. 3, q.), and from the end obliquely (Plate 43, figs. 3, 4, q.). A low broad 
ridge divides the conchiform hollow; the head or “otic process” articulates with the 
squamosal (sq.); and below, there is a bilobate convex condyle for the lower jaw. 
* See Huxley, Proc. Zool. Soc., May 27, 1869, and my papers on the Birds’ skull, namely, “ Ostrich’s 
Skull,” Plate 12 ; “ Fowl’s Skull,” Plates 81 and 87 ; also “ On the Skull of Woodpeckers and Wrynecks,” 
Trans. Linn. Soc. (Zool.), second ser., vol. i., plate 1; and “ On the Skull of Birds,” Part 2, ibid., vol. i., 
plates 20 and 23. 
MDCCCLXXIX. 
4 K 
