Q4 MARION HINES 
which separates the medial limb of the caudate nucleus from the 
middle thalamus ends in the: recessus preopticus and runs along 
the di-telencephalic ventricular junction into the floor of the 
lateral ventricle. The rostral end of the sulcus limitans almost 
reaches it. The dorsal suleus which marks the dorsal border 
of the midthalamus region is almost obliterated. There is, how- 
ever, a little evidence of it at the rostral end of the diencephalon, 
where a small ventricular ridge les on the same level in an an- 
tero-posterior plane with the lateral limb of the velum transver- 
sum. The roof of the diencephalon has become membranous 
just caudal to the velum transversum. 
The angulus terminalis in the telencephalon medium is more 
obtuse. The thin roof of the telencephalon anterior to the 
paraphyseal arch has thickened. The dorsal part of the lamina 
terminalis, the lamina supraneuroporica of Johnston, here called 
the pars tenuis, has increased in breadth measured from the 
midplane to the ventricle and in thickness measured dorso- 
ventrally. This same process has caused an enlargement of 
the lamina terminalis in all directions (fig. 20, Lt., Bailey, ’16a). 
The sculpturing within the telencephalic cavity is so modified 
that the medial and lateral limbs of the caudate nucleus closely 
resemble each other in the extent of their ventricular expansion. 
The lateral ridge of the caudate nucleus is as prominent a hillock 
in the floor of the ventricle as that formed by the medial limb of 
this nucleus. But the greatest change within the ventricle is 
due to the increase in thickness of the medial wall, which les 
ventral to the sulcus limitans hippocampi and cephalad to the 
massive portion of the lamina terminalis, the septum. This 
marked growth of the septal region extends rostrally into the 
base of the evaginating olfactory bulb. The cavity of the ven- 
tricle is almost filled by the lateral choroid plexus. Upon the 
medial wall the developing hippocampus forms a continuous 
bulging on the ventricular wall, long and low at the rostral end, 
sharp and high at the temporal pole. Immediately beneath this 
ventricular ridge is the sulcus limitans hippocampi. The ridge 
is due to a slight infolding of the medial wall, the groove on the 
outer surface being the fissura hippocampi. In this brain there 
