196 NOTE ON THE BRAIN OF HALICORE AUSTRALIS. 



The corpora quadrigemina are not large and ori the median 

 section show that the aqneductus Sylvii extends into a narrow 

 triangular cavity. The posterior wall of the corpora quadrigemina 

 is rather thin. 



The Cerebellum examined from behind is divided into some 10 

 portions (fig. 5) which divisions however, are rather superficial, 

 as can be seen on the horizontal section of cerebellum, (fig. 6) 



The deepest fissures are to be seen on the median section (fig. 

 3 and fig. 4) and divide the cerebellum (examined on the 

 median section) into 3 lobes, of which the anterior is the largest. 

 Corresponding to the lobes the stem of the white substance rami- 

 fying in the arbor vitse is divided into 3 principal branches. 



The pons Varolii is well developed. 



The principal object of the publication of these few remarks about 

 the brain of H. Australis is the hope, that they may induce anato- 

 mists in Australia, who may have ample opportunity (on the coast 

 of Queensland, even in Brisbane) to obtain the Dugong, to fill up 

 the numerous gaps in these notes which being the result of the 

 dissection of one brain are necessarily incomplete. 



EXPLANATION OF PLATE XXIV. 



(All the figures Nat. Size.) 



Fig. 1. — Brain of Halicore Australis, Owen^ from the side. II. — n. opticus, 



v.— n. trigeminus. 

 Fig. 2. — The left hemisphere of the same brain from the other side to show 



the different shape of the deep lateral fissure (fissura Sylvii). I. — 



Tractus olfactorius. 

 Fig. 3. — Rough sketcli of the median section of the same brain made at 



Mabiak, showing the same in situ, in the cranium. The falx is 



covering a great part of the hemisphere. 

 Fig. 4. — The same section, after a photograph taken in Sydney from the 



same object, about four years later. 

 Fig. 5. — Diagramatic view of the cerebeHum of the same brain from behind. 

 Eig. 6. — Horizontsl section of the cerebellum, the position and direction of 



which is indicated by the dotted line (* *) in Fig. L To — Thalami 



optici, cq — Corpora quadrigemina, v — Fourth verticle. 



