226 MR. W. K. PARKER ON THE STRUCTURE AND 
kinds. It is represented here (Plate 33, fig. 5) by the rising on the upper edge of the 
palatine process of the premaxillary (p.p.) close in front of the foremost vomer (v’.). 
Here the posterolateral vomers that bind the hind part of the main vomer (v.) to 
the lateral ethmoidal masses (Plate 33, figs. 5 and 8, v’.) are well developed but not 
large. 
The main vomer of the unripe embryo (Plate 32, fig. 6, v.) was shown to be 
extremely large, thick, and spongy ; now (Plate 32, figs. 5, 8) it is in three pieces, 
and these are not arranged on one plane, as in the Marsupials (which, as I shall show 
in my next paper, have many separate vomers) but the large upper bone (v.) lies in 
the trough of the two lower pieces. These occupy about the first and second third 
of its length (see also fig. 8, showing the hind part of the second lower piece (v’.), and 
the hind third of the main bone v.). 
The subdivision of a primarily single centre is much more frequent in the higher 
Vertebrata than I had imagined, a process curiously in contrast with that more 
familiar phenomenon—ankylosis of primarily distinct bones. 2 
This special peculiarity of the Tenrec, and of the Centetide, generally, as I shall 
soon show, is, after all, merely a modification of the Marsupial type of structure, and 
it is not the only instance in its skull of a new Insectivorous character formed by a 
very gentle modification of an old Marsupial one.* 
I have already referred to the only other splint-bone to be noticed, namely, the 
annulus tympanicus (figs. 1, 8, 4, «.ty.); this, as seen from the inside, separated from 
the skull (figs. 6 and 7, a.ty.), is an imperfect ring of bone, convex on its outer side, 
ribbed at the edge and then scooped on the inner side; it is irregularly crenate on 
its inner, growing edge; its elongated front limb binds strongly on the outer side of 
the huge processus gracilis of the malleus (p.g7.). 
Third Stage (continued).—On the endocranium of the Young Tenrec. 
By a comparison of what is shown in the various figures just referred to we shall be 
able to understand the structure of the inner skull; the younger stage (Plate 32) will 
help us in the interpretation of its parts and regions. 
The snout (fig. 3, ad.n.), as seen from the side, leans over at the fore end; the 
nostril (e.7.) is large, oblique, and well surrounded by a valvular fold ; it is also made 
more complex by an internarial lobe, above. The fenestra in the fore part of the 
septum, seen in the last stage (Plate 32, fig. 6, s.n.), is now filled in with cartilage, 
* The process itself, by which a thick spongy bone splits into concentric lamin, is quite like that 
which is seen in the bark of the Plane tree (Platanus). Considered architecturally, in the building of 
the skull, it is oddly unlike anything wrought by art or Man’s device; and as a mode of the imbrication 
of bony scutes, everywhere, from the Ganoids to the highest Mammals, so familiar to us, this is 
(apparently) unique. The greater part of the huge rounded septo-ethmoidal base, or intertrabecula, 
lies over one large semitubular balk, which is, itself, sheathed by two similar but smaller semitubular 
pieces. 
