CELL MASSES IN THE FOREBRAIN 413 
area in which the cells of the lobe meet those of the pallium above 
in a confused mass. The ventro-caudal margin is not clear. 
Sections give the impression that the pyriform lobe merges in- 
sensibly with the general pallium in this region. In the model 
this boundary has been fixed arbitrarily. 
THE AMYGDALOID COMPLEX 
When the hemisphere of the turtle brain is viewed from the 
lateral and basal aspects (figs. 1, 2, 5, 6) the region which is 
occupied in part by the amygdaloid complex appears as a basal 
prominence similar to the temporal pole of the mammalian brain. 
It is bounded rostrally by the crucial-striatal area, medially by 
the optic tract and thalamus and laterally by the amygdaloid 
fissure. Caudally this prominence passes insensibly into the 
rounded caudal pole. 
Nucleus of the lateral olfactory tract. As above described, 
a part of the lateral olfactory tract bends down across the amyg- 
daloid fissure just caudal to the striatal area and ends in the 
lateral border and rostral tip of the amygdaloid prominence 
(fig. 8). This region is therefore clearly homologous with the 
nucleus of the lateral olfactory tract in the mammalian brain. 
This nucleus is composed of small cells which occupy the tip 
and lateral part of the amygdaloid prominence and extend in a 
thin layer across the amygdaloid fissure to meet in a thickened 
border the large-celled nucleus of the pyriform lobe (figs. 16, 17). 
The two nuclei are separated by a cell-free zone and this con-. 
dition continues back to the end of the nucleus (fig. 13). At 
the caudal border of the striatal area the thin layer of small 
cells is traversed by the fibers of the lateral olfactory tract which 
bend down into this nucleus, and by numerous fibers from the 
pyriform lobe which pass over the surface of the nucleus to join 
the stria medullaris (fig. 56). From the tip of the amygdaloid 
prominence the fibers of the diagonal band go forward as above 
described. These are also mingled with the stria medullaris. 
At the same time the small cells of the diagonal band merge with 
the small-celled nucleus of the lateral olfactory tract (fig. 17). 
