MORPIIOLOGT OF THE BRAIX IX THE MAl\r.M ALIA. 



357 



shorter furrow {y), placed below the displaced upper postsylvian element (/r). This 

 represents another fragment of the postsylvian sulcus. 



In the rig'ht hemisphere the pseudosylvian sulcus is represented by a very shallow 

 depression, which is not worthy to be called a sulcus except in the uppermost 2 millimetres 

 of its extent. The oblique sulcus lo is here joined to the suprasylvian. The sulci x 

 and y are practically symmetrical on the two hemispheres. It seems probable that tlie 

 little ascending branch of the arcuate sulcus in the specimen a belongs to the postsylvian 

 sulcus. In a series of crania of Chlromys which I have examined, the condition of the 

 suprasylvian, pseudosylvian, and postsylvian sulci most nearly resembles that seen in 

 the specimen u in all cases. 



Yig. 35. 



.55. si. 



Fig. 3.J. — Chiroiivjs riKidiiijascnriciisii'. Loft lateral aspect of another brain. 

 Fig. 30. — Chirumijs madagaicitrleusls. Lateral aspect of the right hemisphere. 



In the two crania numbered 302 and 302 B in the Collection of the P^oyal College 

 of Surgeons, the bony ridge corresponding to the suprasylvian sulcus is much nearer to 

 the well-defined ridge representing the pseudosylvian sulcus (in all four hemispheres) than 

 the corresponding sulci are in the brain a. In the skvill numbered 302 the postsylvian 

 ridge seems not to be joined to the suprasylvian. But in the other cranium, as well as 

 in one of those in the British Museum, the suprasylvian and postsylvian ndges unite to 

 form a regular arc. 



In Oudemans's sj^ecimen the arrangement of the sulci appears to have been even more 

 distorted than it is in my specimen /3. Tims on tlie left hemisphere {op. cit. pi. iii. 

 fig. 11) the suprasylvian sulcus (Avhich he labels " Sylvian") is Avidely removed from the 

 small upper fragment of the postsylvian (which he correctly labels " suprasylvia 

 postei'ior "). There is no sulcus corresponding to that which I labelled y (tig. 35), but 

 there is a Avell-defined sulcus x, which Oudemans regards as part of the postsylvian 

 (liis " suprasyl. post."). There are also two furrows radiating from the angle of the 

 rhinal fissure — one (which he does not label) passing to the representative of the svilcus x, 

 and the other (which he calls " Sylvian") passing vertically upward in front oft\\e lower 

 end of the suprasylvian. On the right hemisphere {op. cit. pi. iii. fig. 12) these two 

 sulci (suprasylvian and the last described) are united : the two sulci Avhich appear to 

 represent (this is merely a rough comparison, for no exact homology can exist) the 

 furrows ic and x in my specimen /3 are united to form a very sinuous sulcus. 



