Literary Notices. cxi 



fissures are present ; in gorilla right and orang I right, the superior 

 division is either absent or rudimentary, while in orang II right all 

 three fissures are fused into one. 



2. S. frontalis superior. In most cases [gorilla right, chimpanzee 

 I-IV both, orang la left, orang lb right, orang VI both] this fissure 

 proceeds from the s. prozcentralis superior Occasionally when the prse- 

 centralis is obliterated, this fissure may either extend near to [Orang 

 Ila left] or penetrate [gorilla left, orang la right, orang lb left] the cen; 

 tral fissure. 



3. S. frontalis i?iferior. This fissure proceeds from the lower fis- 

 sura prozcentralis. 1 1 may be feebly developed [chimpanzee I left, 

 chimpanzee III both, gorilla left, orang I right, orang Ila both] or 

 rudimentary [orang VI right] or absent [orang VI left] or fused with 

 the s. rectus [gorilla right, chimpanzee I and II right chimpanzee IV 

 both. 



4. S. frontalis medius. This is present in all [chimpanzee I and 

 II left, chimpanzee III both, orang I right, orang la right, orang lb 

 and Ila both.] It arises from the s. prozcentralis. 



5. .S. rectus. This is present in all. It is identical with the ob- 

 lique frontal fissure of human anatomy. 



6. 6". fronto-orbitahs. This is present in all. 



7. 6 1 . orbitalis. This fissure is feebly developed. It is more highly 

 developed in the gorilla than in any other ape. 



8. Usually this fissure is short [chimpanzee I, III, IV, orang] oc- 

 casionally it reaches almost to the anterior extremity of the cerebrum 

 [chimpanzee II, gorilla.] 



9. S. opercularis. This is found on the lower surface and is 

 straight. 



10. S. subcentralis anterior. This is quite constant. 



In both the chimpanzee and the gorilla, the three frontal convo- 

 lutions have all the distinctive characteristics of the human frontal 

 convolutions. 



The gyrus orbitalis lateralis is identical with the orbital portion of 

 the third frontal convolution. 



There are two fissures (S. opercularis and fronto-marginalis) con- 

 nected with the sylvian fissure of the apes, for which no homologues 

 can be found in the sylvian fissure of man. This fissure differs from 

 the human in passing unobstructedly into the operculum superius. 



The operculum frontale of human anatomy is missing. 



