BRAIN OF A FOSSIL UNGULATE. 891 



the brain-sui'face behind the orbital fissure, where the cast shows 

 the marks of the fronto-parietal suture. 



Posteriorly, between the lateral sulcus and the middle line, 

 traces of a spacious paired vessel {v') are seen. This is formed by 

 two branches, one of which strikes out from the median line, while 

 the other comes inwards and backwards from the surface of the 

 brain. The main trunk, from its direction, seems to have gone 

 round the tentorium and to have joined the transverse sinus. It 

 was probably a vein collecting blood from the superior surface of 

 the hemisphere. 



Cerebellum. 



The general proportions of this part of the brain have already 

 been given. The cast does not, of course, show the minute folding 

 of the cortex characteristic of a fresh specimen, but the main 

 areas and the chief fissures are distinctly marked. 



The most striking featui'e of this organ in Anoplotherium lies 

 in the small size of the lateral lobes. This is probably apr-imitive 

 feature, since, in a comparative series, evolution in the cei-ebellum 

 is chiefly marked by the development of these parts [4]. 



The three fundamental divisions of the cerebellum are indicated 

 by transverse fissures marked on the vermis. 



The Jissura prima is not very clearly shown, but there is a 

 suggestion of a groove in the place where it nearly certainly must 

 have been situated, on the dorsal part of the anterior face of the 

 vermis. 



The Jissura secimda is clearly shown on the posterior surface 

 of the vermis, marking ofi" from the rest of the cerebellum a 

 smooth hemispherical area, which faces posteriorly and is mi- 

 doubtedly the tivula — the anterior division of the lobus posticus. 



The whole of the dorsal part of the vermis belongs to the lohus 

 medius. It is divided into two almost exactly equal parts by a 

 transverse fissure, which can be nothing but the fissura supra- 

 pyramis. The vermis of the median lobe shows a twist such as 

 is seen in a great number of mammals of different groups, and 

 which gives a marked asymmetry to the organ. 



To the sides of the suprapyi'amis — that part of the vermis 

 of the median lobe anterior to the sviprapyramidal fissure — lie 

 triangular depressed areas indicating the exposure of white 

 matter such as is found in many small mammals including most 

 Marsupials, Rodents, Bats, etc. [5]. For this region Elliot Smith 

 has suggested the term " area meduUaris." 



To the sides of the pyramis lie the indefinite masses of the 

 lateral lohes, the small size of which has been commented on above. 

 Their irregular form adds greatly to the asymmetiy of the whole 

 organ. 



To the outside of the lateral lobes lie the probably relatively 

 large fioccular lobes. These can be traced as being connected 

 behind, in the usual manner, to the pyramis. Below, they rest 

 on the periotics and fill in the floccular fossae. Their exact extent 



