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from the Edentate structure manifested by the bones of the foot. But the most 

 remarkable characteristic of the skull of the Glyptodon, by which it differs from 

 the existing Armadillos and approaches the Megatherioids, is the long and strong 

 process in) which descends from the base or origin of the zygomatic process of 

 the maxillary bone. This process is compressed, but in the opposite direction 

 to that in the Mylodon, viz. from before backwards, instead of from side to side : 

 it measures five inches in length from the ant-orbital perforation ; one inch and 

 three-fourths in breadth across the middle : the outer margin is entire, and as if 

 folded back ; the lower half of the inner margin is slightly notched, the extr m'ty 

 of the process curves backwards*. Both anterior and posterior surfaces bear 

 strong marks of the attachment of muscular fibres. The small remaining por- 

 tion of the maxillary bone on the inner side of this process shows portions of 

 three deep sockets o, o, of the same diameter throughout, indicating the implan- 

 tation of molar teeth by a single excavated base ; and showing two longitudinal 

 ridges on both the outer and the inner side, which proves the teeth to have had 

 the same fluted exterior which they present in the lower jaw, and of which the 

 generic name of Glyptodon is expressive. The fractured anterior part of the 

 ' basis cranii ' shows the large cavities for the olfactory bulbs and the remains of 

 a very extensive cribriform plate, the organ of smell being very largely developed. 

 The posterior or occipital surface of the skull slopes forward from the plane 

 of the occipital foramen at an angle of 45° : in the small existing Armadillos it is 

 vertical : in the Glyptodon it is divided by a strong median vertical ridge, and 

 separated by a sinuous, thicker, transverse ridge from the upper surface of the 

 skull. The posterior half of this region of the cranium is marked by the ridges 

 bounding the origins of the temporal muscles, which almost meet along the 

 middle or sagittal line. Part of the lambdoidal suture is seen at p ; the other 

 cranial sutures are obliterated. The temporal fossae are pierced by numerous 

 large vascular foramina. The anterior parts of the temporal ridges q diverge to 

 the posterior angles of the supra-orbital ridges. The frontal or inter-orbital 

 part of the upper surface of the cranium is broad, and nearly flat, smooth and 

 slightly concave at its posterior half, slightly convex, rough and perforated by 

 vascular foramina at its anterior half. The most prominent parts, above the 



* The extent of this process is shown in the reduced side-view of the skull in Plate I. 



