102 
PEOFESSOE OWEN ON THE SCELEDOTHEEE. 
The first peculiar character which the entire cranium of the Scelidothere presents is 
the increase in vertical diameter (if the thin pterygoid plates be excluded), from the 
occiput (3,4) to the anterior nostril (is, fig. 2 , Plate VIII.): this character appears to be 
due, mainly, to the depth of the upper jaw required for the lodgement of the molar teeth 
and their persistent pulps. 
The occipital condyles (Plates VIII. and IX. 2 ), though terminal, are less prominent than 
in the Mylodon or Megathere : they are relatively wider apart : their inner straight sides 
converge towards their lower end. The foramen magnum (Plate IX. 0) is wider relatively 
than in the Megathere : its upper boundary is festooned, a median notch dividing two 
convex curves of the thin and rather prominent border : just within this border are two 
pits : on the inner side of each condyle is a depression : the inner sides of the occipital 
foramen are impressed with the oblique canals leading to the precondyloid foramina, 
The plane of the foramen magnum forms, with that of the basioccipital, an angle of 135°. 
The occipital region, which was vertical in the young specimen first described, inclines 
a little forward, as it ascends, in the adult skulls, but to a less degree than in the Mega- 
there : its height from the upper border of the foramen magnum is half its breadth • 
it is bisected by a strong median vertical ridge, with a small venous foramen at its lower 
end : an arched semicircular thicker and rougher ridge forms its upper and lateral 
boundaries : this ridge bifurcates at its lower part on each side, intercepting thereby a 
narrow longitudinal fissure, corresponding with the wider lateral fossa of the occipital 
region in the Megathere, but here rather resembling the digastric fissure in ordinary 
mammals : the fissure is contirrued into the rough interspace between the mastoid and 
paroccipital. In each moderately concave division of the occipital region there is a low 
sub vertical lateral ridge, which is nearer the outer boundary than is the corresponding 
ridge marked e in the skull of the Mylodon, in Plate V. fig. I, of my “ Memoir on the 
Mylodon,” 4to, 1842. 
The paroccipital (Plates VIII. and IX. 4) is relatively larger than in the Megathere, the 
mastoid ( s ) is relatively smaller : there is no second superoccipital ridge as in the Mega- 
there. 
The lateral rough surfaces (Plate IX. r) for the attachment of the 7‘ecti capitis antici 
muscles to the basioccipital, are less prominent than in the Megathere : the under sm-face 
of both the basioccipital ( 1 ) and basisphenoid ( 5 ) is fiatter : the lateral basisphenoidal 
protuberances are low and obtuse, relatively larger than in the Megathere, not angular 
as in the Mylodon. 
The precondyloid canals are relatively smaller than in the Mylodon; their outlets 
(ib. y>), as in that animal, are behind and distinct from the foramen jugulare or foramen 
lacerum (^‘), not blended therewith as in the Megathere. 
Corresponding with the indication of the smaller size of the tongue thus given by the 
canal for its muscular nerve, is the less relative size and depth of the stylohyal depression 
( 8'). The carotid canal (c) seems to have begun at the fore-part of the foramen lacerum. 
The rough bifid under surface of the petrosal (le) divides it from the auditory cawty. 
