OF THE SKULL IN THE COMMON SNAKE. 
413 
lies directly beneath the nasal, and above the maxillary, the homology will at once 
be seen. 
There they are mere muco-dermal bones, enclosing part of the net-work of the 
mucous glands of the head, where the “lateral line series ” breaks up into rows. In 
the Amphibia and Reptiles they are specialized — -just as other dermal bones are 
specialized — and assist in walling-in and flooring the more and more perfect nasal 
labyrinth. * 
Here, in the Snake all the slime-glands appear to be concentrated into one on each 
side (Plate 33, figs. 9-12, n.g.), and these glands find a place under the olfactory 
pouches — involutions of the antero-inferior regions of the face. 
Moreover, the bone which I seize upon in the Siluroid Clarias capensis as the fore- 
runner of the reptilian septo-maxillary is the “ os-terminale ” of the sub-orbital series 
of slime-bones, as the “ nasal ” of the fish is the “ os-terminale ” of the super-orbital 
series. 
Seen from the inside (Plate 33, fig. 1G, s.mx .) the septo-maxillary is a flat wedge, 
broad behmd and pointed in front ; this flat inner face is separated from the septum 
nasi by the thick sub-mucous stroma (Plate 33, figs. G-14, s.mx., s.n.). 
Its upper surface is sinuous (figs. 6-15) for at its broadest part, where it forms a lid 
to the vomerine dish, containing the kidney-shaped gland, it shelves downwards, is 
gently convex and then rises into the nasal wall (figs. 9-11), and also grows round 
the side of the gland. In front (figs. 6-8) it is a mere splint ; behind (figs. 13-15) 
it is a thick plate. 
The vomer is related to the lower edge of the septum (figs. 7-14, v.) ; on its inner 
face it is flat, but has a larger and more irregular surface than the septo-maxillary 
(fig. 16, v.). 
Below (Plate 32, fig. 3, v.) it shows three parts : an anterior spike ; a middle bowl ; 
and a hinder ear-shaped lobe. The bowl (see also Plate 33, figs. 2 and 15, v.) is 
notched for the duct of the gland and the second labial (see also figs. 10, 11). 
Thus in some of the sections (figs. 11, 12) we apparently have two bones ; these, 
however, are only parts without and within the notch. 
Where the duct passes out (fig. 11, d.n.g.) there the gland is most accurately 
encapsuled ; the septo-maxillary, as a lid, with its rising outer and inner edges, covering 
the gland, which is embraced by the curling laminae of the vomer both without and 
on the inner side. 
The copious illustrations of this pleasing piece of morphology will make the above 
description quite intelligible. 
* In the Herring and its congeners, the maxillary bone carries two bones on its back ; the hinder of 
these looks forwards, and forms an acute angle with the free end of the maxillarjr : this is the jugal. The 
other forms an acute angle with the fore part of the bone, and almost a right angle with the j ugal : this is 
the p re-orbital, which takes on the curious specialization in the air-breathers by which it becomes the 
septo-maxillary.” 
