46 JorUNAI. OK CoMl'AltA I I\'l-: NErR()l.()(,\ . 



Lateral v'lc-v (Plate V, Figs, i, 4). — Viewed from the 

 side, the outline of the avian prosencephalon is composed of 

 the following curves: 



I. A convex curve, which extends caudo-dorsad from the 

 cephalad to the dorsad extremity of the prosencephalon, 

 where it turns and passes caudo-ventrad to the caudad ex- 

 tremity of the prosencephalon. Here the curve turns again, 

 and, for a short distance, passes cephalo-ventrad. 



z. A broken line, composed of two or three convex 

 curves, which extends cephalad from the end of the above 

 curve to the cephalad extremity of the prosencephalon. 



In the lower types of avian brains, the cephalad portion 

 of curve number one slopes more gradually towards the base 

 of the brain than it does in the higher types.(') 



Dorsal Jissure. — This fissure is universally present, but is 

 not always in the same position (Plate V, Figs, i, 4, 5, 6, 

 7,8, 10; DF). 



In the Anatidce (Plate V, Fig. 5, DF), this is a convex 

 curve, which lies upon the dorsal surface of the prosenceph- 

 alon. It arises from the meson at about one-third of the 

 length of the cerebrum from the cephalad extremity of the 

 brain. For more than half of its course, this curve passes 

 caudo-laterad; then it passes caudo-mesad to the caudad ex- 

 tremity of the cerebral hemisphere, where it merges into that 

 border of the hemisphere. The greatest width of this curve 

 is equal to about one-half of the greatest width of the cere- 

 bral hemisphere. 



In the Icteridtv (Plate V, Fig. 7, DF),this curve is also 

 convex; but it has its origin upon the ventral surface of the 

 brain. Slightly caudad to the rhinencephalon, it arises from 

 the meson and extends cephalo-laterad for a short distance, then 

 it passes caudo-dorsad to the dorsal surface of the prosen- 

 cephalon. 



I According to A. liiiiiim, this is also Hue of tlie brains of liuropean birds. Op. cit. , 

 p. 4J8-439. 



