158 DR. C. F. SONNTAG 01V THE 



The Hard Palate (Plate I. B). 



The hard palate is 2 - 7 cm. long, "8 cm. wide between the first 

 pair of teeth, 1 cm. wide between the second pair of teeth, and 

 •7 cm. wide between the last pair, so it first expands and then 

 contracts. It is encircled just internal to the teeth by a series of 

 palatal tubercles which, however, have no counterparts on the 

 dorsum of the tongue. On each half of the palate there are 

 seven of these — one opposite each tooth, one anterior to the first 

 tooth, and one at the side of the mid-line : the first and second 

 are borne by the premaxillae. The tubercles increase in size from 

 before backwards, and the fifth pair is the largest. 



The palate has the same chocolate colour as the labial margins. 

 Running along the mid-line is a white streak which sends out 

 branches to end on the mesial sides of the tubercles. In the 

 posterior part this streak overlies the crest shown in Plate I. C. 



When the mucosa is removed from the subjacent bone, it is 

 seen that the palatal tubercles do not cover bony eminences, and 

 the bone differs greatly from that of Choloepus (Plate I. D). 



In B. tridactylus there is a strong median crest on the posterior 

 half, and there is a gutter on each side of that ridge. Anteriorly 

 each gutter is converted into a tunnel by a fenestrated bridge of 

 bone ; the tunnel on the right side reopens on to the free 

 surface, but the left one does not. Both gutters, however, com- 

 municate posteriorly with the nasal fossa?. 



In the mid-line in front there is a groove which widens from 

 behind forwards, but, as the premaxillae were lost in the pre- 

 paration of the skull, I am unable to give a complete description 

 of it. 



The bone is much perforated by small foramina. Some of 

 these open into the afore-mentioned tunnels and the others into 

 the nasal cavity. 



No sutures are present outlining the various elements com- 

 prising the bony palate as in Choloepus. 



The bony palate of Choloepus differs in many ways from that 

 of Bradypus. It is much larger and its constituent bones are 

 clearly outlined by sutures. There is no gutter nor ridge on the 

 posterior part, but many foramina of different sizes are present. 

 Of these, there is a large pair on the palate bones lying posterior 

 to the fifth pair of teeth, and a large pair on the maxillae 

 in front. The former, probably, correspond to the gutters of 

 Bradypus. 



The Soft Palate. 

 The soft palate, which measures P2 cm. from before back- 

 wards, is pink in colour. It is attached to the posterior extre- 

 mity of the hard palate in front, and to the prominent pterygoid 

 plates laterally. No hamular pterygoid processes are palpable 

 through it, but the convex free borders of the plates can easily be 

 felt. Its posterior edge is concave backwards, and its oral surface 



