77 



FOSSIL MAMMALIA. 



which determine its affinities amongst the Edentata, there next remains to be 

 considered the relative position, extent, and connections, of the different bones 

 composing the cranium. 



The occipital bone constitutes the whole of the posterior, the usual proportion 

 of the inferior, and a small part of the upper and lateral portions of the cranial 

 cavity : there is a small descending ex-occipital process immediately exterior to 

 the condyle : above this part the occipital bone is articulated to the mastoid process 

 of the temporal, and the supra-occipital plate is joined by a complex dentated 

 lambdoidal suture to the two parietals, without the intervention of interparietal or 

 Wormian bones; the course and form of the lambdoidal suture is shown inPl.XXII ; 

 it has the same relative position as in the Orycterope ; in the Armadillos, the 

 suture runs along the angle between the posterior and superior surfaces of the 

 skull. The thickness of the occipital bone, at this angle, in the Scelido there, 

 exceeds an inch, and its texture consists of a close massive diploe, between the 

 dense outer and inner tables, (PI. XXIII. fig. 1.) 



The squamous portion of the temporal bone has a very slight elevation, not 

 extending upon the side of the cranium more than half an inch above the zygoma ; 

 it is thus relatively lower than in the Orycteropus ; but is similarly bounded above 

 by an almost straight line, (PI. XXI., fig. 1.) The mastoid process is small, 

 compressed, with a rounded contour ; immediately internal to it is a very deep 

 depression, corresponding to that for the digastric muscle. But the most 

 interesting features in this region of the temporal bone consist in the free 

 condition of the tympanic bones, and the presence of a semicircular pit, imme- 

 diately behind the tympanic bone for the articulation of the styloid element 

 of the hyoid or tongue-bone : in these points we trace a most remarkable corre- 

 spondence with the Glossothere, and in the separate tympanic bone the same 

 affinity to the Orycteropus, as has been already noticed in the more bulky extinct 

 Edental. 



This correspondence naturally leads to a speculation as to the probable generic 

 relationship between the Glossothere and Scelidothere : now it may first be 

 remarked that the styloid articular depression is relatively much larger and much 

 deeper in the Glossothere than in the Scelidothere ; in the former its diameter 

 equals, as we have seen, one inch ; in the Scelidothere it measures only a third of 

 an inch, the whole cranium being about two-fifths smaller ; if we turn next to the 

 anterior condyloid foramina, which in the Scelidothere are double on each side, 

 we obtain from them evidence that the muscular nerve of the tongue could only 

 have been one-third the size of that of the Glossothere. These proofs of the 

 superior relative development of the tongue in the Glossothere indicate a differ- 

 ence of habits, and a modification, probably, of the structure of the locomotive 

 extremities ; and when we associate these deviations from the Scelidothere, with 



