106 
PEOFESSOE OWEN ON THE SCELIDOTHBEE. 
downward and backward, rapidly expands, decreasing in thickness, and bifurcates. One 
branch ascends with a slight twist, forming the suprazygomatic process (s), and haring an 
obtuse rudiment of the true zygomatic process (z) on its posterior border. The suprazygo- 
matic process appears, in the natural position of the bone, to touch or rest upon the end 
of the zygomatic process of the temporal (27). The descending process (d) is broader and 
thinner ; is gently concave, is directed obliquely downward and backward, and tenninates 
obtusely. 
The cranial cavity is 7 inches in fore and aft extent, including the cavity occupied by 
the olfactory ganglions, which is inch long : the greatest transverse diameter of the 
cavity is 4 inches 9 lines, which corresponds with the back part of the cerebral hemispheres. 
A low tentorial ridge is continued from the upper edge of the petrosal, in a dhection which 
shows that the cerebellum lay wholly behind the cerebrum ; but the major part of the 
tentorium was membranous, as in the Sloths and true Ant-eaters, not osseous as in the 
Manis. In the Orycteropus a sharp bony ridge extends from the petrosal into each side 
ot the tentorium. The greatest vertical diameter of the cerebrum of the Scehdothere 
appears to have been 2^ inches ; that of the cerebellum and medulla oblongata 2 inches 
3 lines : the transverse diameter of the cerebellum was about 3 inches 9 lines, its fore 
and aft diameter about 2 inches. The inner surface of the cranial cavity indicates several 
convex masses of cerebellar convolutions, and also a few simple parallel longitudinal con- 
volutions upon the upper and lateral parts of the cerebral hemispheres. 
The small relative size of the brain of the Scelidothere is most clearly demonstrated ; 
it was scarcely one-fourth part the length of the skull: both this proportion and the 
relative position of its principal masses, succeeding one another lengthwise as in reptiles, 
closely accord with the low general condition of the cerebral organ in the existing species 
of the Order Bruta. 
The upper part of the basisphenoid is impressed with a broad and shallow ‘sella 
turcica,’ bounded laterally by two grooves leading forwards and inwards from the carotid 
foramina. The line of junction between the basisphenoid and basioccipital is indicated 
by a slight transverse elevation which bounds the ‘ sella ’ behind : a low median protu- 
berance forms the anterior boundary : there are neither anterior 'nor posterior clinoid 
processes. External to the carotid canal there is a wide groove leading to the foramen 
ovale. This foramen (Plate VIII. fig. 2 /), though absolutely less than in the INIylodon, is 
relatively larger as compared with the precondyloid foramen, and indicates that the tongue 
was more sensitive and less muscular or bulky in the Scelidothere ; but, m reasoning 
Irom the size of the foramen ovale, it must be kept in mind that certain branches both 
of the second and third divisions of the fifth pair’ of nerves were associated with the per- 
sistence of large dental pulps of which they regulated the formative force. Anterior to 
the foramen ovale, and at the termination of the large common groove lodging the trunk 
ot the fifth pair of nerves, is the inner orifice of the canal representing the foramen 
rotundum (ib. r ) ; the diameter of this canal is 5 lines, bemg somewhat less than that of 
the foramen ovale. 
