188 PHYSIOLOGICAL SERIES. 



D. 226. The brain of a Flying Phalanger (Petaurus breviceps). 

 In all respects like a small specimen of Trichosuru*. 

 [The olfactory bulbs are lacking in this specimen.] 



O.G. 1323 BC. 

 Gervais, Nouv. Arch. Mus., t. v. 1869, p. 243. 



D. 227. The brain of a Koala or Australian " Native Bear" 

 (Phascolarctus cinereus) ( ) . 



The most noteworthy feature of this brain, as in Dendro- 

 lagus (D. 221), is the paucity of sulci in such a relatively 

 largo neopallium. 



The few sulci which are found are exceedingly variable, 

 and it becomes very difficult to determine their homologies 

 with any certainty. 



The most pronounced sulcus (in this specimen) ascends 

 from about the mid-point of the rhinal fissure, and may 

 possibly represent the Carnivore pseudosylvian sulcus. In 

 many cases, however, it is quite insignificant and does 

 not join the rhinal fissure. In such cases there is often a 

 much deeper sulcus behind it, which Ziehen calls " Sylvi;m."' 



In front of these pseudosylvian sulci there is a very 

 faintly marked orbital (presylvian) sulcus. 



In addition very shallow furrows traverse all parts of 

 the neopallium. 



The dorsal commissure is very small. The hippocampus 

 presents the typical Marsupial arrangement. 



There is a short calcarine (splenial) sulcus, which cannot 

 be seen in this specimen. 0. C. 1323 A r. 



Ziehen, Jenaische Denkschr., Bd. vi. 1897, p. 98. 



Elliot Smith, Journ. Anat. & Phys., vol. xxxiii. 1898, p. 30. 



D. 228. The brain of a Koala (PJiascolarctus cinereus), ( ? ). 



The sulci are much more imperfectly developed in this 

 specimen. There is a pseudosylvian sulcus on the left 

 hemisphere only. 0. 0. 1323 A s. 



D. 229. Casts of the cranial cavities of two skulls of the extinct 

 Thylacoko carnifex. 



The s;ime peculiar, broad, flattened shape which charac- 

 terise.- the lniin of Phascolomys is also presented by these 



