DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 
73 
the front of the presphenoidal region to the end of the snout, and of the basicranial, 
from the former point to the foramen magnum, are nearly equal; so they are in the 
embryo, and in the new-born, Unau. 
But in the great Ant-bear the front measurement is about three tunes the length 
of the hinder; hence I call this little skull quasi-embryonic —the Myrmecophagine 
specialization of the face is arrested, and it is, very probably, the descendant of a 
much larger type, with a much longer face. 
The fore part of the face is bent downwards in a manner that is abnormal for this 
advanced stage, although it would be quite normal for an early embryo. The snout 
( al.n .) is compressed and the nostrils ( e.n .) lateral; the premaxillaries (px.) are very 
small angulated bones just touching the nasals above, and followed by the maxillaries, 
which for them, have a starved appearance ; they are wrinkled, and hollow externally, 
without much convexity in the alveolar region. The infraorbital foramen is oval, and 
the bone over this passage swells somewhat, but has a notched upper margin where 
the lacrymal (7.) rests upon it. The maxillary is notched again, twice, in its sub¬ 
orbital region, and then ends in an ear-shaped jugal process, with fine threads of bone 
—remnants of the jugal (j.) —attached to it. 
The lacrymal (l.) is a thin shell of bone, perforated for the duct (J.c.), and hollow 
towards the eye-ball; it has both a facial and an antorbital region. The frontals 
are almost Ophidian; together they nearly form a cincture by the large develop¬ 
ment of their orbital plates, which leave no space for any “pars plana” of the 
ethmoid, or allow more than a small patch of the low orbitosphenoids (o.s., see fig. 7) 
to be seen in the base of the orbital region. 
These orbital plates come down to rest upon the palatines (figs. 1 and 3, pa.), and 
form a moderately concave wall to the very indefinite orbit. The supraorbital region 
is marked by a convexity having the shape of an hour-glass, the “waist” of which is 
part of the general constriction of the skull round the enclosed ethmoids. 
The greatest concavity of the deep orbital plate is just below the second supra¬ 
orbital swelling; it is then a little convex, and then hollows out backwards and 
downwards, the hollow ending in the principal orbital foramen, for the ophthalmic 
(orbitonasal) nerve (V 1 .). There the orbitosphenoid (o.s.) is exposed, and in it the 
optic passage (II.) is seen. 
Behind the sinuous imperfect coronal suture the parietal (p. ) stretches backwards 
to the occipital arch, and, below, comes down towards the floor of the skull nearly as 
well as in the Snake. 
Thus the temporal fossa is merely a part of the general face of the skull, infero- 
laterally, the parietal being scarcely at all hollowed to form it; here, at the lowest 
front angle, the parietal sends forwards a large round lobe that binds down upon 
both the wings of the sphenoid just over the sphenoidal fissure (V 1,2 ‘). 
Looking towards the mid-line, below, we see the undergirders of the skull—the 
palatines and pterygoids (pa., pg.); they show, from this aspect, their ribbed edge, and 
MDCCCLXXXV. L 
