530 DR. R. W. SHUFELDT ON THE COMPARATIVE OSTEOLOGY [ Apr. 27 
so feebly developed as to be barely noticeable, while the sqgwamosal 
process below it is rather long, though extremely slender. The 
valley between them is only fairly well-marked. Humming- 
birds exhibit similar characters with respect to these two apo- 
physes, but, taken as a whole, there is nothing, beyond the big 
pars plana in one of this family, to remind us of the orbital 
cavity as a whole in drachnothera. To be sure, the anterior wall 
of the brain-case is deficient in bone in both, markedly so in the 
Trochilidee, but, in so far as that goes as indicating any athnity 
between the two groups, it stands for very little. 
The external aural aperture in the skull of Arachnothera is 
large, and admits of a full view of the interior of the bony ear. 
Posteriorly, and to some extent below, this entrance is protected 
by a thin scroll of bone, seen in so many other passerine forms, 
and very prominent in the Trochilide * # Among some of the 
Ceerebide, as, for example, in Diglossa bar itula, these bony parts 
of the external ear are remarkably developed ; the aperture upon 
either side looks directly to the front, while the bulbous, thin, 
and scroll-like wall protecting it above, behind, and below isa 
striking feature upon this aspect of the cranium. 
Posteriorly, the skull of Avrachnothera ofters but little for 
examination beyond what we would find in the skull of any 
ordinary passerine bird. The occipital ridge is but faintly defined, 
while the supra-occipital prominence is above the average in size, 
and especially so in A. longirostris. Thisis also seen in Z’rochilus, 
whereas among the Meliphag gidee it is not the case. 
Passing to the basis cranii we have tomote the large subcireular 
foramen magnum, and the extremely minute occipital condyle, 
which is distinctly hemiglobular in form. The basitemporal area 
is smooth and convex throughout, presenting at the usual 
localities the foramina for the entrance and exit of vessels and 
nerves to and from the cranial cavity. The double entrance to 
the Eustachian tubes, one to either side, is shielded below by 
a very narrow rim of bone. The basi-pre sphenoidal rostrum 
presents nothing peculiar, and is thoroughly coéssified anteriorly 
with the mesethmoid and the pars plane. 
The quadrate possesses a sharp, compressed orbital process, that 
in articulation comes in close contact with the cranium. Its 
mandibular facet for the lower jaw is double, there being a small 
mesial elliptical facet and an outer and larger irregular-shaped 
one. A longitudinal groove stands between them. As usual, the 
mastoidal articular head is double, and the bone, as a whole, is 
highly pneumatic. Apart from the quadrates, all the other 
osseous structures at the base of the cranium in Arachnothera are 
characterised by extreme slenderness and delicacy of structure. 
And, in passing, it may be said that all the articulations, 
* Suuretptr, R. W. “Contribution to the Comparative Osteology of the 
Trochilide, Caprimulgide, and Cypselide.” P. Z. S. Lond., Dee, 1, 1885, pl. lviii. 
fig. De 
