398 PHYSIOLOGICAL SERIES. 



rounded " folia," whereas the paraflocculus is a great pro- 

 jecting mass of folia arranged in a feather-like pattern. 

 Unlike the condition found in most mammals with projecting 

 lobules (compare Tamnnduas), almost the whole of the 

 paraflocculus contributes to form the so-called "petnxal 

 lobule" in this case. 0. 0. 1337 o. 



D. 573. The brain of a young Red Howler (Alonatta senicula). 

 The left cerebral hemisphere has been separated. 



The sinuous intraparietal element of the Sylvio-intra- 

 parietal complex ends in a bifid manner so as to form a 

 small transverse occipital sulcus. There is, however, a 

 well-developed coinpensatory-intraparietal sulcus behind 

 the central and parallel to the main intraparietal element. 



There is a long deep sulcus parallel to the caudal part of 

 the " parallel " sulcus, which can only be the Simian sulcus. 

 There are small and faintly-marked inferior occipital, 

 inferior temporal, and collateral sulci ; and at the point 

 toward which these three sulci converge there is a peculiar 

 deep irregular pucker. The meaning of this is not quite 

 clear, but it is significant that the inferior occipital may, in 

 different brains, be confluent with either of the other two 

 sulci. Here all three sulci are poorly developed, and this 

 peculiar depression makes its appearance apparently as a 

 compensatory factor. 



There is a simple linear orbital sulcus and an equally 

 plain external compensatory-orbital, which we can now have 

 no hesitation in calling fronto-orbital. This is the lowliest 

 Ape in which this sulcus (which in the Man-like Apes 

 marks the anterior boundary of the insula) has been 

 observed. 



The sulci upon the mesial aspect of these hemispheres 

 are particularly interesting. Although the calcarine sulcus 

 (unlike that of D. 572) has a bifid extremity, its caudal limbs 

 are so small that they produce no mechanical disturbance. 

 The parieto-occipital sulcus is broken up to an even greater 

 extent than in specimen D. 571. The notch in the superior 

 border is present only on the left hemisphere. The calloso- 

 marginal sulcus joins the " compensatory " sulcus, and the 

 latter is quite separate from the small detached parieto- 



