74 R- J- Anderson, 



"the superoccipital is almost flat in Cynocephalus porcarius, but sloping 

 upwards and backwards forms an acute angle with the parietal, from 

 which it is divided by a strong ridge where the diploë are obliterated" 

 (Owen). The flat occipital of Gorilla (above the foramen) is a good 

 example of masking the posterior convexities. In Cebus and Callithrix 

 the occipital has two large depressions, whilst in Mycetes it is flat 

 and vertical. In Ateles the Paroccipitals form rough tubercles. Owen 

 mentions that the superoccipital in the Aye-aye is a "thin plate 

 moulded on the middle and lateral lobes of the cerebellum, and 

 showing outwardly their respective prominences." In Simla and Tro- 

 glodytes the plane of the occipital forms an open angle with the basi- 

 occipito-sphenoidal line. The participation of the occipital in forming 

 the roof of the skull is evident on inspection, but still more striking 

 in making the necessary measurements. The paroccipitals are not 

 found in the old world monkeys nor in Cebidae. Muscle pressure 

 seems responsible for the thinning. Meckel found the superoccipital 

 developed from a single centre in mammalia generally, but in man 

 frequently from four centres, two above and two below. Modern 

 researches bear this out, although the traces of the division are apt 

 to disappear. Meckel believes these elements are very frequent. The 

 inter-parietal bone of Mammalia is regarded by some as an occipital 

 element. It is probable that the four tabular elements are in response 

 to the conditions of the cerebrum and cerebellum, at least in some cases. 

 The mesial prominence is lost in man, also a ridge for fibrous tissue 

 is left. In the skull of a young Chimpanzee a slightly raised eminence 

 reminds one of the transverse eminence seen in the upper part of the 

 Papuan's skull, mentioned by Professor Krause. The ridge at the 

 base of the Mastoid in Troglodytes is carried to the occipito-parie.tal 

 suture internally. It is likely that a ridge may develop temporarily 

 and change as the habits of the animals change within certain limits. 

 Waldeyer describes a retro-mastoid process in the Papuan. The 

 length and breadth of the condyles vary a good deal and the distance 

 between the condyles in front as compared with the distance behind. 

 Professor Calori pointed out that strictly speaking two condyles on the 

 occipital bone are not always a mammalian character, nor a single 



