OF GALLINACEOUS BIRDS AND TINAMOUS. 195 
with it, are quite free of the frontals, which do not reach this vertical bar of the 
cranio-facial axis. Combined with this peculiarity there is mostly a feeble growth of 
the orbital plates of the frontal, and a very minute development of the orbito-sphenoidal 
lamin: this gives rise to the curious openness in the dry skull at this part. These 
upper orbital fontanelles are seen in many adult birds. In the old Grouse only the 
anterior part of this space is open, as the superethmoidal fontanelle (Pl. XXXVI. fig. 9); 
in younger birds the upper orbital fontanelles are also seen, but periosteal layers of 
bone fill up the space in the course of time. This pyriform fontanelle of the Pigeon, 
Plover, and Hemipodius opens into the skull at its hinder broad part, and into both 
orbits anteriorly (Pls. XXXIV. XXXV.&XXXVII._ In all these things the Syrrhaptes 
is intermediate between the Pigeon and the Grouse. The descending plate of the 
presphenoid of the Syrrhaptes (Pl. XXXVI. fig. 4) is very thin, but forms a more 
perfect junction with the great bony bar below than in the Pigeon and the Hemipodius. 
The subtypical Grouse, e.g. Zetrao tetrix, 7. urogallus, and ZT. cupido, Lagopus scoticus 
and L. cinereus, and Bonasia europea, all show an advance of the typical group in the 
ossification of the antorbitals ; but the Zalegalla is in advance of them. In the Pigeons, 
the Hemipodii, and the Syrrhaptes (Pl. XXXVI. fig.4) we have a very perfect state of 
the ossification here—fusion of these parts taking place least in the Pigeon, and that bird 
having the descending plate of the lachrymal largest in proportion to the antorbital. 
In all these birds there is more or less obliteration of the suture between the upper and 
lower prefrontal plate (‘‘ antorbital ” and ‘‘ aliethmoid”’), and with the lachrymal. All 
this thick mass of bone in front of the eye, and over which the nasal nerve and olfac- 
tory lobes pass, is in these three groups extremely thick and spongy, and not thin and 
fibrous as in the Grouse. In them all, but least in the Pigeons, these curious bony 
air-cells take up much of the room which should be occupied by the olfactory laby- 
rinth; and in all of them the angle between the crura of the nasal is partly filled up with 
the cellular ala of the great central ethmoid. In the Plovers these ale are less ossified 
and altogether less pneumatic than in the Pigeon and its allies. In the adult skull of 
these latter birds the cellular, broad frontal portion of the nasals melts insensibly into 
the frontal bones (Pl. XX XVII. fig. 8), and on each side of the tumid top of the ali- 
ethmoid there is a slender fibrous crus; the inner crus runs alongside the nasal pro- 
cess of each premaxillary ; the outer runs downwards and forwards to join the pre- 
vomer and the angle of the premaxillary. The latter bone is not only thoroughly 
Pigeon-like in Syrrhaptes, but it is indeed somewhat of a caricature of what we see in 
the Common Pigeon (Columba livia). In the latter bird the true “ neb” or solid part 
of the premaxillary is very small and feeble; and then the lateral rami are pinched 
inwards ; so that the whole face is not only feeble, but also compressed (Pl. XX XVII. 
fig. 8, px.). In the Syrrhaptes and in the Dodo this takes place to a much greater 
extent, and the narrowing is sharp and sudden; it is a very elegant structure, how- 
ever, as may be seen by referring to Strickland and Melville’s Plates of the Dodo, and 
