Glossotherium, in forming part o f the circumference o f an ellipse, whose long axis
is v e r tic a l; and in sending outwards, from its anterior part, a convex eminence,
which terminates in a point directed downwards and forwards.
Such appear to be the most characteristic features o f the cranial fragment
under consideration, in which we have found, that the articular surface for the os
hyoides throws more light upon the nature o f the animal o f which it is a part,
than even the glenoid cavity itself. There now remains to be described as much
o f the individual characters o f the constituent bones as the specimen exhibits.
The occipital bone, besides forming the posterior and part o f the inferior
parietes o f the cranium, extends for about h a lf an inch upon the sides, where the
ex-occ ipital element is articulated by a vertical suture with the mastoid element
o f the temporal: this suture is situated in a deep and well-marked muscular depression
(e, fig. 1), measuring three inches in the vertical, and upwards o f one inch in
the transverse direction. T h e other sutures, uniting the occipital to the adjoining
bones, are obliterated. T h e breadth o f the occipital region must have exceeded
the height o f the same by about one-third. The condyle extends nearly to the
external boundary o f the occipital aspect o f the cranium; there is situated,
external to it, only a small ovate, rounded and smooth protuberance. Th e slightly
concave surface o f the occipital plane o f the cranium is bounded above b y a thick
obtuse ridge, the muscular impressions are well sculptured upon it. It is traversed
transversely at its upper third b y a slightly elevated bony cr est; and the surface
below this ridge is again divided by a narrower intermuscular crest, which runs
nearly vertically, at about an inch and a h a lf from the external boundary o f the
occipital plane. A s a similar crest must have existed on the opposite side, the
general character o f the occipital surface in the Glossothere would resemble that
o f the Toxodon. A similar correspondence may be noticed in the terminal
position o f the condyle, and the slope o f the occipital plane.
Above the transverse ridge, the rough surface of the occipital plane slopes
forward, at a le ss obtuse angle with the basal plane, to the first named ridge
which separates the occipital from the coronal or superior surface o f the skull.
The contour o f this surface runs forwards, as far as the fragment extends, in
an almost straight l in e : the ex tent o f surface between the temporal muscular
ridges must have been about five inches posteriorly, but it decreases gradually
as it extends forwards: all that part which is preserved is quite smooth. The
attachment o f the fasciculi o f the temporal muscle, and the convergence o f their
fibres as they passed through the zygoma are well marked on the sculptured
surface of the bone. The zygomatic process is relatively stouter than in Orycteropus:
it is prismatic: the external facet is nearly plane: the superior is concave,
and increases in breadth anterio rly : the inferior surface offers a slight
convexity behind the flattened articular surface for the lower jaw. The margin
o f the zygoma formed by the meeting o f the upper and lower facets presents
a semicircular curve, extended transversely from the cranium, and directed
forwards.
Th e anterior extremity is obliquely truncated from below upwards and
forwards, and presents a flattened triangular surface indicative o f its junction
with an os malee: the space between this extremity and the side o f the cranium
measures one inch and nine lines across, and thus gives us the thickness of the
temporal muscle. The distance from the origin o f the zygoma to the occipital
plane is relatively greater than in Orycteropus; Glossotherium is in this respect
more similar to Myrmecophaga and Mauis.
The sphenoid bone forms a somewhat smooth protuberance below and behind
the base o f the zygoma. T he tympanic bone is wedged in between this protuberance
in front, and the mastoid process behind. The ch ie f peculiarity o f the broad
mastoid is the regular semicircular cavity at its under part for the articulation
o f the styloid bone o f the tongue. Th is depression is separated below by a
broad rough protuberance from the foramen jugulare, (J\ fig. % PI. X V I ,) which
is immediately external to, and slightly in advance o f the great foramen con-
dyloideum, c. A small rugged portion o f the os petrosum separates the jugular
from the carotid canal, wliich arches upwards and directly inwards to the side of
the shallow sella turcica, (the external and internal orifices o f the carotid canal
are shown at g , figs. 2 and 3). The ch ie f protuberance on the basis cranii is a
large and rugged one, serving for the attachment o f muscles, and due chiefly to
the expansion o f a great sinus in the body o f the sphenoid. Th is protuberance
is separated from the smaller sphenoid protuberance before mentioned by a
large groove continued downwards and forwards from the tympanic cavity, and
containing the Eustachian tube, which does not traverse a complete osseous
canal. Immediately internal to the glenoid cavity is the large orifice o f the canal
transmitting the third division o f the fifth pair o f nerves, the principal branch o f
which endows the tongue with s en sib ility ; this foramen (A, fig. 2) is rather le ss
than that for the muscular nerve o f the tongue.
The internal surface o f the present cranial fragment affords a very sa tisfactory
idea o f the size and shape o f the brain o f the extinct spe cie s to which it
belongs. It is evident that, as in other Bruta, the cerebellum must have been
almost entirely exposed behind the cerebrum; and that the latter was o f small
relative size, not exc eeding that o f the A s s ; and chiefly remarkable, as in the
Orycterope, Ant-eater, and Armadillo for the great development o f the olfactory
ganglia. The antero-posterior ex tent of the cribriform plate, as exposed in this
fragment, is three inches, and the complication o f the cethmoid olfactory lamellae
whicli radiate from it into the nasal cavity is equal to that which ex ists in the
smaller Edentata (fig. 3, PI. X V I ). Th e nasal cavity is complicated in Glosso