458 THE VERTEBRATE SKELETON. 



In Choloepus the symphysial part is drawn out in a somewhat 

 spout-like manner (fig. 91, 6). In both genera the thyro-hyals 

 are ankylosed with the basi-hyal. 



5 



FIG. 91. SKULL OF A TWO-FINGERED SLOTH (Choloepus didactylus) x \. 

 (Camb. Mus.) 



1. anterior nares. 4. angle of the mandible. 



2. postorbital process of the 5. jugal. 



frontal. 6. spout-like prolongation of the 



3. coronoid process. mandible. 



In Megatherium the general appearance of the skull is 

 distinctly sloth-like, but the facial portion is more elongated, 

 partly owing to the development of a prenasal bone, and the 

 zygomatic arch is complete. The mandible is very deep in the 

 middle, and is drawn out into a long spout-like process in front. 



Anteaters (Myrmecophagidae) have a much modified skull, 

 and this is especially the case in the Great Anteater, Myrme- 

 cophaga. The skull is smooth and evenly-rounded, in these 

 respects recalling that of Echidna, but it is longer and tapers 

 much more gradually than in Echidna. The occipital condyles 

 are remarkably large. The premaxillae are small, and the 

 long rostrum is chiefly composed of the maxillae and nasals 

 with the mesethmoid and vomer. The zygomatic arch is 

 incomplete, and there is no trace of a separation between the 

 orbit and the temporal fossa. The palate is much elongated, 



