408 PHYSIOLOGICAL SERIES. 



D. 590. The brain of a Geoffrey's Spider-Monkey (Ateles geof- 

 froyi). 



This is a smaller amj simpler brain than the last two. 



The frontal region resembles that of specimen D. 588. 



In addition to the chief parieto-occipital sulcus (which 

 has only a short dorsal course in front of the intraparietal 

 sulcus, where it ends in a bifid manner) there is a second, 

 shallower, vertical accessory parieto-occipital sulcus behind 

 the occipital part of the intraparietal sulcns. The latter is 

 not joined by its superior post-central ramus (the chief 

 element of which has an unusually sagittal direction). 

 Anteriorly it appears to join the Sylvian fissure : posteriorly 

 it dips into the Simian sulcus and its termination is thus 

 hidden from view. 0. C. 1337 H d. 



D. 591. The brain of " Ateles" species unknown : the left hemi- 

 sphere has been detached. The ramus postcentralis superior 

 of the intraparietal sulcus is triradiate and not joined to the 

 rest. 



There is a well-developed ramus occipitalis (transversus) 

 of the intraparietal sulcus which lies in front of and parallel 

 to the Affenspalte and behind the extensive parieto-occipital 

 sulcus. So that the typical relations of these three sulci 

 are demonstrated (especially on the left side) with dia- 

 grammatic clearness. 



The calcarine has but very short limbs of bifurcation and 

 seems to be joined by the parieto-occipital sulcus, as some- 

 times happens in the human brain but exceedingly rarely in 

 the Apes. And the collateral sulcus is composed of inner and 

 outer parts, of which the inner approaches, but does not quite 

 reach, the stem of the calcarine sulcus. 0. C. 1337 H c. 



D. 592. The brain of a Long-haired Spider-Monkey (Ateles vel- 

 lerosus). The left hemisphere has been detached. The 

 membranes have not been removed. The backwardly- 

 directed branch of the arcuate sulcus is detached on flic 

 right side, but on the left is continuous with the rest of 

 the sulcus. 



The superior limiting sulci of Keil (Marchand's opercular 

 sulci) are again partially exposed. 0. C. 1337 Ha 



