310 DR. A. KEITH ON THE CHIMPANZEES. [Mat. 7, 



the long nasal bones of the lower CatarrhinI ; in all the other 

 Anthropoids and in Man they have undergone marked retro- 

 gression, especially in the Orang. The nasal bones, as can be 

 seen in the living Chimpanzee, extend downwards to the level of 

 the lower border of the orbit and are never over 25 mm. long ; 

 ill the Gorilla they extend much lower down and are never less 

 than 40 mm. in length. The nasal bones of the Gorilla show a 

 sharp median ridge, evident in the living animal. This ridge 

 appears at adolescence and sometimes disappears in very old 

 animals. A trace of this ridge is seen on the nasal bones of the 

 Central-African Chimpanzee. The nasal bones unite before birth 

 in the Gorilla, at or after birth in the Chimpanzee. At their 

 upper end the nasal bones of the Gorilla always project within 

 the interfrontal sutnre, sometimes to a slight degree, frequently 

 to a very considerable extent, and at their lower ends unite into a 

 spine in over 60 per cent, of skulls. On the other hand, the nasal 

 bones of the Chimpanzee seldom project within the interfrontal 

 suture and only to a slight extent, the examples occurring mostly in 

 Central-African Chimpanzees, and show an inferior spine in only 

 15 per cent, of skulls, and these were mostly from Central Africa. 

 The inrer-oi'bital breadth and the shape of the bridge of the nose have 

 frequently been used as characters of differentiation. They both 

 depend on age, and to some extent on sex. All through the life 

 of a Chimpanzee the bridge of the nose keeps changing in con- 

 formation, owing to the continual growth of the lachrymo-ethraoidal 

 air-sinus : the convex bridge of the young adult becomes converted 

 into the flat or depressed bridge of the old adult. The inter- 

 orbital breadth is practically the same for Gorillas and Chimpanzees, 

 being greater in males than females, but the bridge of the nose 

 in the Gorilla never becomes flattened and depressed like that of 

 the Chimpanzee. 



In her wide, smooth, rounded alar nasal folds, Johanna, and 

 all the Chimpanzees ascribed to the variety of which she is an ex- 

 ample, shows a marked Gorilline feature. A. niger never possesses 

 these folds so markedly, although they do increase in size with 

 age ; but in the Gorilla they extend almost to the margin of the 

 lip, the middle part of which shows a widely grooved philtrum. In 

 Johanna a distinct transverse groove marks the upper lip from 

 the nose, and such a groove occurs always in Chimpanzees. The 

 middle and inferior turbinate bones of the Chimpanzee are more 

 convoluted than in the Gorilla, and the nasal duct less inflated. 



In development, the palatine processes of the palate-bone of 

 the Gorilla frequently fail to meet, giving rise to a form of cleft 

 palate ; they always, when they unite, leave an open angle between 

 them : the corresponding processes in the Chimpanzee are always 

 well developed and unite so as to leave the bony palate with a 

 transverse postei-ior border. The nasal spines of the premaxilla are 

 commonly present in the Gorilla (17 out of 28) and seldom in the 

 Chimpanzee (5 out of 43). The nostrils are \^ddest in the Gorilla. 

 The anterior opening of the nasal cavity in the adult Chimpanzee 



