NO. 4 AN ENDOCRANIAL CAST GAZIN II 



and posterior fissura of Adapis, which Edinger (1929) has interpreted 

 as the ff. praecentralis inferior and sylvian, were not developed in 

 Smilodectes. These greatly affect the outline and form of the Adapis 

 endocast. It should be noted, nevertheless, that a small notch far 

 forward on the anterolateral margin of the Smilodectes endocast may 

 be in the position of the praecentralis inferior but more probably 

 corresponds to the rhinal fissure. 



A particularly striking detail apparent in Neumayer's ventral view 

 of the Adapis endocast is the markedly obtuse angle between the faces 

 of the petrosal fossa, with the posterior surface of the temporal lobes 

 facing decidedly outward. In Smilodectes this surface is nearly per- 

 pendicular to the median vertical plane of the skull. Also noticeable in 

 this view and perhaps better demonstrated in Hofer's photograph 

 (1962, fig. 2c), is the relatively much longer rhinencephalon anterior 

 to the pyriform lobes and much greater separation between the optic 

 chiasma and hypophysis in Adapis. Moreover, the pedestals represent- 

 ing the apertures of the floccular fossa and internal auditory meatus 

 are relatively larger in proportion to the size of the cast than in 

 Smilodectes gracilis whose brain size is seen to be actually larger 

 than in Adapis parisiensis, as determined by the scale of Neumayer's 

 illustrations. 



Illustrations by Le Gros Clark (1934, fig. 48; 1945b, fig. 1; and 

 1959, fig. 121) of an endocranial cast in the British Museum, evidently 

 of a different individual than that figured by Neumayer, show some 

 detail possibly not evident in the other cast. These include representa- 

 tion in the dorsal view (1945b and 1959) of a lateral sulcus as well as 

 of the pseudosylvian, and possibly better development of the anterior 

 lobes of the neopallium (1945b). Moreover, the proportions of the 

 cerebellum are more clearly depicted in Le Gros Clark's figures, show- 

 ing that the cerebellum was relatively more elongate than in Smilo- 

 dectes. The actual size of the British Museum specimen is not evident 

 as the indicated scales for Le Gros Clark's figures are not in agree- 

 ment. 



