BRAIN OF A FOSSIL UNGULATE. 88^ 



position, relation to the rhinal fissure, and its possible connection 

 on the right side to the lateral sulcus are exactly like the con- 

 ditions in the brain of Orycteroims. 



Behind the orbital, the side of the hemisphere is marked by a 

 clearly defined sulcus, rather under 2 cms. in length, and running 

 obliquely from behind forwaixls and downwards to join the orbital. 

 This sulcus is nearly certainly the coronal. Its relations on the 

 two sides are similar, but while on the left it is simple, on the 

 right it forks slightly at its su.perior or dorsal end, and in its 

 middle length it is connected with a very short horizontal sulcus 

 (6), the identity of which is not clear. 



There is no trace of a pseudosylvian sulcus on either side of 

 the brain. 



Dorso-laterally the neopallium is marked by a sulcus which, 

 starting at the back of the hemisphere, runs straight forward, 

 23aralle] to the middle line, for about 2 cms., and then, curving 

 down towards the rhinal fissure, ends on the right side, about 

 7 mm. from that fissure, but on the left actually joins it, or very 

 nearly so. This must be the suprasylvian sulcus. Though small 

 and nob so strongly arcuate as in the higher Ungulates, it is of 

 the typical Ungulate form in the strength of its posterior branch . 

 Near its caudal end the posterior limb of the suprasylvian is 

 joined by a very short sulcus (c), wliich lies external to it. This 

 sulcus, though minute, is. constant on both sides. 



Midw^ay between the suprasylvian sulcus and the rhinal fissure, 

 and within the curve of the formei', there is a short deep hori- 

 zontal sulcus about 5 mm. long on the right side, and about twice 

 that length on the left. This sulcus is exactly analogous in 

 position to a similar short one in Oryctero'pus. For purposes of 

 I'eference it will be spoken of as sulcus " rZ," 



On the dorsal surface of the neopallium (text-fig. 157, p. 890), 

 running in general parallel to, and on an average about 7 mm. from, 

 the middle line, is a deep sulcus, which extends from very near the 

 olfactory peduncle to the posterior surface of the hemisphere. 

 This long furrow bears several branches and is really comjDound. 

 On the left side of the brain, the most anterior part of it, about 

 1 cm. long, lies further from the middle line than the rest of the 

 furrow, and was probably not directly continuous with it, though 

 in the cast there is a connection by means of a shallow depression. 

 This short sulcus must be the frorean. On the right side it is 

 directly continuous with the rest of the sulcus, which is clearly 

 the lateral. The relation between the prorean and lateral sulci 

 is exactly as in Orycteroptis. 



The large lateral sulcus, though roughly parallel to the middle 

 line, is by no means straight, and pursues a sinuous course along 

 the hemisphere. On the right side it has two very shoit branches 

 going outwards from it, at distances respectively of 1*5 and 

 3"3 cms. from its caudal extremity. 



At the junction of the prorean and lateral sulci on each side 

 there is another sulcus, a few millimetres in length and running 



