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that they appertain to a species of the same genus. The portion of the 

 cranium includes the parietes of the left side of the cerebral cavity, the 

 corresponding nervous and vascular foramina, the left occipital condyle, 

 a portion of the left zygomatic process, and fortunately also the left 

 articular surface for the lower jaw. The condyles of the occiput are wide 

 apart, sub-elliptic, very similar in position, form and relative size to those 

 in Orycteropus. The foramen occipitale is transversely oval ; its plane 

 slopes from above downwards and forwards at an angle of 40° with that 

 of the occipital region of the skull. The occipital plane is bisected by 

 a mesial vertical ridge : there is a less developed transverse curved inter- 

 muscular crest, which runs parallel with and about half an inch below 

 the marginal ridge ; the surface of the occipital plane on the interspaces 

 of these ridges is irregularly fitted with the impressions of the insertion 

 of powerful muscles. The upper surface of the cranium is smooth and 

 regularly convex. 



The extent of the origin of the temporal muscles is defined by a slightly 

 raised broad commencement of a ridge. The zygomatic process of the 

 temporal commences posteriorly about an inch and a half from the 

 occipital plane : its origin or base is extended forwards in a horizontal 

 line fully four inches, where it terminates as usual in a thin concave edge. 

 The free portion of the zygoma, continued forwards from the outer part 

 of this edge, is a slender sub-compressed process, half an inch in the 

 longest or vertical diameter, and less than three lines in the transverse ; 

 the extremity of this process is broken off: the opposite extremity of 

 the molar portion of the zygoma is entire and obtusely rounded. The 

 articular surface beneath the zygoma for the lower jaw is flat and even, 

 with the outer and inner margin slightly bent down, but having no de- 

 finable anterior or posterior limits; its breadth is two inches. 



The loose bony frame of the membrana tympani describes rather more 

 than a semicircle, having the horns directed upwards : it has a groove, 

 one line in breadth, along its concave margin for the attachment of the 

 membrane, and sends down a rugged process, half an inch long, from its 

 lower margin. The tympanic bone in the existing Sloths long maintains 

 a similar detached condition as a bony hoop. In the Dasypodes and 



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