37 



Order EDENTATA. 



Tribe Pkyllophaga. 

 Family Gravigrada. 



Genus Megatherium. 



218. The anterior or facial part of the skull of the Megatherium Cuvieri, in- 

 cluding the anterior terminations of the temporal ridges, the anterior 

 part of the orbits, the sockets of the two anterior teeth and a consider- 

 able portion of the intermaxillary bones. The convergence of the tem- 

 poral ridges as they ascend from the post-orbital tuberosities shows that 

 the extent of origin of the temporal muscles is relatively greater than in 

 the Mylodon, or other known Megatherioid quadrupeds ; these ridges 

 are, in fact, represented as meeting on the upper surface of the skull in 

 the Madrid specimen. The larger proportional length of the teeth, 

 which causes a greater depth of both upper and lower jaws in the Mega- 

 therium than in its congeners, makes the lower jaw relatively heavier, 

 and thus necessitates the superior size of the temporal muscles. There 

 is no trace of a distinct lachrymal bone. The malar process of the su- 

 perior maxillary bone is short, but deep, and presents a rough and irre- 

 gularly indented surface, for the articulation of the malar bone, which the 

 Madrid specimen shows to be large and complicated. The malar process 

 of the maxillary is perforated by three ant-orbital foramina, bearing about 

 the same proportional size to the skull, as does the corresponding single 

 foramen in the Tapir. The fronto-maxillary suture may be traced from 

 below the post-orbital tuberosity, crossing obliquely the upper end of 

 the malo-maxillary articulation, and extending forwards to the middle of 

 the lateral margin of the nasal cavity, of which the frontal bone con- 

 tributes a portion, for the extent of nearly two inches, and thus separates 

 the maxillary from the nasal bones. The transverse suture between the 

 nasal and frontal bones may be traced, though partly obliterated, 6ve 

 inches anterior to the orbits. The nasal bones, which have been con- 



