THE GREAT CHIMPANZEE. 401 



Between the foramen caroticum and the foramen stylo-mastoideum in the Chimpanzee, 

 there is a deep stylohyal fossa (38, Pi. LXIII.) answering to the root of the stylohyal in 

 Man ; this is less deep and less constant in the Orang. 



The mastoids are relatively larger in the Chimpanzee, and develope a true process 

 instead of a rough oblong tract. 



The glenoid articulation of the squamosal is more concave, especially from side to side, 

 in the Chimpanzee, and it rises above the level of the tympanic meatus. In the Orang 

 the surface is almost flat, and is carried below the level of the auditory process ; the 

 inner process of the glenoid cavity is wanting in the Orang, but the hinder one is as 

 large as in the Chimpanzee. 



In the Chimpanzee a styliform process of the sphenoid (6 s) abuts against the inner 

 glenoid process (g), and is wedged between this and the eustachian process (e) of the 

 petrosal. In the Orang the styliform process is absent. 



In the Chimpanzee the pterygoids are narrower than in the Orang, the external plate 

 is less developed, and the internal plate is thicker and shorter : a ridge is continued 

 from the base of the external plate into the styliform process in the Chimpanzee : the 

 pterygoid fossa is deeper and longer in the Orang. 



The posterior nostril is shorter and wider in the Chimpanzee. 



The bony palate is longer and shallower in proportion to its width in the Chimpanzee ; 

 it is more e.vpanded anteriorly in the Orang. In the Orang the two posterior palatal 

 foramina are nearer each other, and have two tuberosities between them ; these are 

 absent in the great Chimpanzee. The prepalatal foramen is larger and more distinctly 

 divided in the Chimpanzee. There is a moderate-sized foramen on each side nearly in 

 the line of the obliterated premaxillary-palatine suture, the course of which is marked 

 by two or three small foramina in the Orang. 



The incisors are thicker from before backwards in proportion to their breadth in the 

 Orang than in the Chimpanzee. 



The interspace between the incisors and canines is narrower in the Chimpanzee, but 

 the canines have longer and broader crowns in the Chimpanzee. 



The outer lobe of the first premolar, p 1 , is larger than the inner one, and vice versd 

 in the second premolar, p 2, in the Chimpanzee : the outer lobe of ;> 1 is a Uttle larger 

 than the inner one, and both lobes are equal in p 2 in the Orang. 



The antero-posterior diameter of the true molars is greater in comparison with the 

 transverse diameter in the Chimpanzee than in the Orang, and the last molar is more 

 equal in size and similar in structure to the others ; hence the longitudinal extent of 

 the series of grinding teeth, including the premolars, is longer; the five teeth in the 

 Orang equalling only the last four teeth in the Chimpanzee. 



The structure of the grinding surface of the true molars is so modified in the Orang 

 as to deviate further from that in Man than it does in the Chimpanzee : both the first 

 and second true molars have the four principal cusps in the Orang, but they are less 



