NERVOUS SYSTEM. VERTEBRATA. 223 



The anterior rhinal fissure is horizontal and forms an 

 angle of about 120 with the posterior rhinal, which crosses 

 on to the ventral surface at a point midway between the 

 vallecula Sylvii and the caudo-ventral angle of the hemi- 

 sphere. 



On the right hemisphere (fig. 95, reversed) there is a deep 

 triangular depression communicating with the bend of the 

 rhinal fissure. From the apex o this depression a very 

 short sulcus (not more than 5 mm. long) extends upward 

 and slightly backward ; this undoubtedly corresponds to 

 the so-called " Sylvian fissure " of Bradypus and Felis. 



Fig. 95. (x.) 



SULC.DIAG. SULC.COR.LAT. SULC. SUPRAS. 



SULC.PROR. 



SULC.ORB..-X j\ 



"SULC. P. SYL. 



OLF. TUBER. PYR.L. 



There is a short suprasylvian sulcus joined to a much 

 longer postsylvian (or " posterior suprasylvian " as it is 

 more generally called). In front of the suprasylvian sulcus 

 there is a small deep sulcus analogous to the diagonal of 

 Bradypus and the Carnivores. 



There is a long, deep, presylvian or orbital sulcus ; it is 

 separated by a short interval from the anterior rhinal fissure 

 and is joined to the prorean sulcus (vide the Carnivora), 

 near the interhemispheral cleft. 



There is a long, deep, lateral or conjoint corono-lateral 

 sulcus in the posterior two-thirds of the hemisphere, and 

 two short and relatively shallow post-lateral sulci behind it 

 parallel to the postsylvian sulcus. 



There is a deep, vertical calcarine sulcus on the medio- 

 caudal aspect of the hemisphere. As in the Sloths it does 

 not join the intercalary sulcus, which is represented in this 

 hemisphere by two shallow sulci. 



