OF GALLINACEOUS BIRDS AND TINAMOUS. 217 
of the Tinamou. This bone, the prevomer, is not a rhinal element—a true turbinal, 
nor the homologue of the prefrontal of the fish (see Owen, Report on Archetype, p. 220), 
but a splint applied to the cartilaginous floor of the anterior nostril, and only existing in 
birds and certain groups of Reptiles, and in the Amphibia. In the Tinamou the pre- 
vomer runs forwards as a sharp wedge between the palatine process and the dentary 
margin of the premaxilla, to within 7 lines of the end of the beak: it is made of just the 
same delicate fibrous bone (Pl. XL. fig. 1). It gradually becomes 2 lines in width, and 
then divides into a long zygomatic and a short palatine process: close behind this 
bifurcation the zygomatic process thickens and gives off two secondary processes, one 
upwards, which articulates, as we have seen, with the descending crus of the nasal, 
and one inwards, a flat zigzag band of bone (Pl. XL. figs. 1 & 2), which becomes pedate 
and then articulates with the anterior part of the palatine, by curving downwards and 
applying itself to the inner edge of that bone. On the whole, the bone of the Tinamou 
agrees closely with its counterpart in the Ostriches; yet the inner process is some 
approach to the same part in the Grouse and the Sandgrouse ; but in them the body of 
the bone is reduced to the smallest dimensions, and the inner process passes far more 
mesiad of the palatine bar, and is free and straight, although pedate. In the Ostriches 
the inner process is scarcely differentiated from the rest, and the body of the bone in 
them is of most unusual size. The ascending process of the prevomer is the homo- 
logue of that curling outward part of the bone in the Python which seemed to Professor 
Owen to have ‘‘ aneurapophysial relation with the olfactory nerves ’’ (ébid.). 
Our author atones for this mistake, at the top of the next page, by satisfactorily deter- 
mining the great preorbital bones of the Python to be merely the lachrymals, and not 
the ‘‘ anterior frontals ” as Cuvier supposed. 
Across the mid region of the palate of the Tinamou there has been an unusual 
amount of anchylosis even for a bird (fig. 2) ; and here we impinge upon the Apteryax 
in a manner not to be misunderstood. This is the more interesting, as this bird is four- 
toed; and if any one will also compare the leg and foot of the two birds, they will see 
how very gentle a change is required to convert either the leg or the beak of an Apteryx 
into that of a Tinamou. 
The zygomatic process of the prevomer has coalesced with the slender jugal (Pl. XL. 
figs. 1,2, 3), and this latter hone reaches, as in other “‘ Struthionide,’’ nearly to the os 
quadratum, the quadrato-jugal being a small piece of bone passing somewhat within the 
jugal ; it is, however, separate in the adult. These bones vary greatly in different birds, 
and in the Fowl-tribe the quadrato-jugal reaches nearly to the angle of the premaxilla. 
Where the maxillary exists at all, it is quite external to the prevomer, which is always 
placed mesiad of the dentary part of the premaxilla, of the maxilla itself, and of the 
quadrato-jugal. The absence, for the most part, of the maxillary gives rise to an 
extraordinary and somewhat vicarious development of the prevomer in birds. In the 
2F2 
