110 
MR. W. K. PARKER ON THE STRUCTURE AND 
Plate 15, fig. 1) is finished on the inside in its hinder half, by a 'precurrent cartilage, 
which overlaps the recurrent tract ( pc.c ., rc.c.). This stoutish rod, which ends hr 
a point hr front, is a direct ongrowth from the inner edge of the nasal floor, over 
which floor the copious folds of the so-called “ middle turbinal ” are to be found. 
Behind these precurrent spikes, the proper olfactory floor, formed by a large ingrowth of 
the aliethmoidal fold ( al.e .), is a wide sinuous tract, convex towards the inside, and at 
the outside, but convave along the middle. This wide part is divided, by a renewal of 
the concavity, into two lobes, the inner of which lies on a lower plane than the outer, 
and reaches a little further back. The inner part of the inner lobe is hollowed out, 
the nasal floor running upwards, in a concave manner, to reach the vomer. The outer 
and higher lobe is rather uncinate, hooking a little towards the orbitosphenoidal 
region; it is the lower face of the great lateral ethmoidal mass, seen from above in 
fig. 2. 
The main median investing bone, the vomer (v.), and the small paired anterior bones 
(V.), were not peeled off with the rest of the superficial bones, when the preparation, 
here figured, was made. The large parosteal tract (v.) has been dominated by two very 
distinct endoskeletal structures, namely, the intertrabecula, and the floor of the 
double nasal labyrinth. This large, long vomer reaches by its hind forks as far as 
the labyrinth, whose halves it unites, below ; in front, it runs nearly as far as to 
Jacobson’s organ. It is cleft, behind, up to its middle, the cloven part having the 
keel divided, which has run back from the fore half. In the foremost part the bone is 
simply rounded, running thence to its grooved upper face, on which the front partition 
wall rests. 
This very remarkable foliacious vomer (Plate 14, fig. 5 ; Plate 15, figs. 1 and 3, v.) 
is roughly pointed in front; then at the beginning of its second third it gives off a 
narrow wing, right and left, and these wings widen up to the median slit; a little 
behind it they end. Overlapping them, another pair of wings arise, right and left, 
twice as wide, and then another pah- wider still, which run on to the diverging end 
of the forks, behind ; the left middle wing is perforated. 
The vomer is pinched in under the first and last wing, wffich are thinnish, as is 
usual in the edges of the Mammalian vomer (Plate 1 5, fig. 3, side view) ; but the 
middle wing is a solid mass with an oval outline. 
This lobe or wing did not peel away easily, like the other, as is usual with a paros- 
tosis in its relation to the underlying cartilage, but had to be broken away, there 
being no line sharply dividing the bone-cells from the cartilage-cells. Thus the 
vomer is here grafted on to each moiety of the cartilaginous nasal capsule at the inner 
edges of its floor, as in Passerine Birds.* 
* See Nitzsch, article “ Passerinee,” in Eksch and Gruber’s ‘ Encyclopasdie,’ 1840; “ Ueber die Fainilie 
der Passerinen,” Zeits, fur die gesammten Natnrwiss., 1862 ; Huxley, Proc. Zool. Soc., April 11,1867, pp. 
450-454; and my papers on the AEgithognathous type of skull, Trans. Zool. Soc., vol. 9, plates 54—62, 
and vol. 10, plates 46-54 : Trans. Linn. Soc., ser. 2, Zool. vol. i., plates 20, 21; and Monthly Micros. 
Joum., 1872, plates 34-39 ; and, ibid., 1873, plates 8-10. 
