88 PROF. W. K. PARKER ON THE STRUCTURE 
On the Investing Bones displayed in the transversely-vertical sections, 
By going over the figures of these sections in detail, we shall recapitulate what has 
been said of this system of bones; the reader will compare these illustrations with those 
showing the skull in various aspects. 
Section 1 (Plate XVIII. fig. 1).—This is through the fore part of the skull, and shows 
how the maxillaries (ma) embrace the premaxillary (px), especially below ; besides the 
sharp dentary edges of the former, the upper part of each bone has begun to form the 
large supracranial valley. 
Section 2.—Here (fig. 2), in front of the outer nostrils (e. m), the maxillaries (ma) are 
scooped in forming the passage, and are two-winged; they are crested above, have a 
ridge below the crest, and are cultrate at their inturned lower edge. The premaxillary 
(2. px) is now asmall wedge between the upper part, only, of the two bones, above the end 
of the nasal pouches. Below, an oblique wedge of bone is seen; this is the large left 
fork of the vomer (v) cut through. 
Section 3.— Here (fig. 3) the skull was divided through the nostrils (e.); and thus 
the maxillaries (ma) are seen in two parts on each side. The premaxillary (n. pa) has 
thickened again; and the right, or lesser, fork of the vomer (v) is cut through as well as 
the larger spur. 
Section 4.—In this section (fig. 4), which is also through the nostrils (e. 2), the nasals 
(7) are cut through at their foremost pointed end ; the other parts are closely like what 
was shown in the last. 
Section 5.—Here (fig. 5), close behind the nostrils, the vomer is cut through behind 
its notched part; it is hollow both above and below, and much wider in the latter region. 
There is here a definite space between the vomer and the inner edge of each maxillary 
bone (mr); and the nasal and intermaxillary wedges (n, n.p2) are larger. 
Section 6.—In this section (fig. 6) two pairs of new bones are cut through; it was 
made through the widest part of the hinder pouches. ‘The cranial trough is now 
very large and deep; for above the maxillaries (ma) a pair of large, solid, obliquely- 
crested bones have come into view. These are the prefrontals(p,f'). The sharp wedges 
of the nasals and premaxillaries (n, ». px) only cover the middle part of the nasal roof 
(al.sp) ; there is here only a fibrous mat (n.f) over the nasal sacs, right and left. Below, 
the vomer has given place to the upper processes of the palatines (pa), which are thick 
styles: the maxillaries are here thick slabs of bone, sharp above, subcultrate below, 
and having a sharp process running inwards, the rudiment of a palatine plate. Between 
the wall and this partial floor the ethmo-palatine (e.pa) is lodged, just as the “ pro- 
rhinal” is lodged between the lamin of the premaxillary in a Batrachian. 
Section 7.—This slice (fig. 7) is from behind the nasal pouches, and also behind 
the nasals and premaxillaries. Here the frontal (/') comes in at the mid line, and it 
forms the keystone to a low inverted arch, the piers of which are the large, diverging, 
sinuous prefrontals (p,f); the frontal is here subconvex above and carinate below. 
