20 C. JUDSON HERRICK 



Figs. 2 and 3 Figure 2 is a view of the brain of Xecturus seen from behind and 

 slightly from above, to illustrate the foi-m of the recessus lateralis rhombencephali 

 and its walls. Fig. Sis a key drawing to figure 2. X 8. (The peculiar shape of the 

 cerebrum in this figure is due to the fore-shortening resulting from viewing the 

 specimen almost directly from behind. Dorsal, ventral and lateral views of the 

 entire brain of Necturus are given by Kingsbury '95, and more detailed dorsal and 

 ventral views by McKibben '13.) 



The plexus chorioideus of the fourth ventricle has been removed. At the cau- 

 dal end of the figure the cross section shows two ependymal sulci in the floor of the 

 ventricle on each side of the medial ventricular sulcus. The inner one of these 

 is the sulcus limitans (s.l.), separating the motor area from the sensory area; the 

 lateral one (.s./aL) forms the medial boundary of the acoustico-lateral area. The 

 area acustico-lateralis extends forward neai'ly to the tip of the auricular lobe. 

 At a point between the V and VII roots it is separated by a transverse ependymal 

 sulcus into anterior and posterior lobes (cf. fig. 1). The lateral wall of the reces- 

 sus lateralis is formed chiefly by the lobus anterior of the area acustico-lateralis 

 and its antero-medial wall by the body of the cerebellum. The walls of the anter- 

 ior diverticulum are composed of massive but thin cerebellar tissue of very undif- 

 ferentiated type. The positions of the frenulum of the velum medullare anter- 

 ius and decussatio veli are indicated by the attachments of the IV nerves. 



