20 G 
MR, W. K. PARKER OK THE STRUCTURE AND 
Shrew; and this both in the dissections (Plate 29, figs. 4, 5), and the sections 
(Plate 30). 
Where the perfect narial floor ends, there on each side of the intertrabecular base of 
the septum (Plate 29, figs. 4, 5, s.n.), a gradually increasing wing is given off, which, on 
reaching the notch in the premaxillary—between the dentary margin and the palatine 
process—at once expands, hooks itself round the front of the opening of Jacobson’s 
organ, and then completely surrounds that organ for a short distance. The rest of 
the cartilage is like the bowl of a spoon, and protects the organ infero-externally. 
Along the inside of each retral tract the palatine process of the premaxillary (p.px.) 
runs as a vertical lamina, connate, apparently, as in the Mole, with the anterior 
paired vomers. Between the hinder third of these laminae the fore part of the long, 
normal, main vomer (v.) is seen. The inferior turbinal is developed from the inside of 
the lower edge of the nasal wall ( al.sp .) ; the upper and middle turbinals (fig. 4, 
al.e., m.tb.) from the inner face of the capsule in its dilated part. There, for some 
distance, the floor is very deficient, the wall, simply bending inwards, with a sinuous 
selvedge underneath ; at the end it finishes in a sort of pouch, right and left of the 
forks of the vomer. 
Where a kind of secondary desmog natliism is made bj 7 the vomer (as in Passerine 
Birds), there a small oblong tract of bone runs in between the main vomer and the 
ossifications already forming in the nasal wall and floor; these little bones are the 
posteriorpaired vomers (v".). Behind the short exposed tract of the perpendicular 
ethmoid (p.e.) the small crescentic presphenoid ( p.s .) is seen, with its concavity looking 
backwards ; a tract of cartilage, larger than this bony centre, separates it from the 
next bony tract—the basisphenoid ( b.s.). 
The semiosseous orbitosphenoids are partly hidden in this view, but are fully shown 
in the upper (fig. 3). The posterior sphenoid is well displayed in this aspect. The 
basal bone (b.s.) is inordinately large for a Mammal, but small and aborted for an 
Insectivore. It is, roughly, an equilateral triangle, with its hinder angle truncated, 
and its anterior side transverse to the cranial axis; the imperfect lateral margins are 
sinuous, so that there is a rounded lobe at each angle; this is the arrested “ tympanic 
wing.” The alisphenoids (al.s.) are sutured to the fore edge of this lobe, right and 
left, and run forwards and a little outwards; their rounded fore angle is not quite 
ossified. 
Each bone is a rough, notched, snaggy wedge ; the notch is on the outer margin, 
just a little in front of the projecting hinder angle or lobe. This is the imperfect 
foramen ovale (V 3 .); it is a large vacuity, as seen from below. The scarcely ossified 
fore end is rounded on its inside ; it reaches to the middle of the incurved nasal 
floor (cd.e.) much beyond, and some distance below, the orbitosphenoid (o.s.); the 
inner margin is notched both at this front part and at the hinder third. There is a 
considerable membranous space between the alee and the narrow fore part of the base, 
right and left. 
