188 G. ELLIOT SMITH. 
small transverse layer (/. sup.), which Burckhardt calls the 
lamina supra-neuroporica, and describes as ‘ ein kurzer 
ependymatoscr Abschnitt, . . . der erste Abschnitt der Scheitel- 
platte.” All authorities now seem to agree in regarding this 
as the anterior extremity of the roof (Deckplatte). This 
must be admitted if the angulus terminalis is really the dorsal 
extremity of the “ vordere Schlussnaht.” The lamina supra- 
neuroporica takes a sudden bend backwards (fig. 3) to form a 
horizontal band, which gives origin in many lowly Vertebrates 
to the plexus inferiores, and in higher animals to the 
plexus laterales as well, or exclusively. In the specimen 
under consideration, however, although the plexus laterales do 
not actually spring from this lamina, they are formed from the 
caudal prolongations of its lateral parts (vide fig. 15) on 
either side of the paraphysis (par.). Immediately dorsal to 
this lamina the anterior wall of the third ventricle is bulged 
out to form a large sac (fig. 2, par.), which constitutes the 
paraphysis of Selenka, of which a fuller description will be 
given below, 
The whole extent of the roof (actual) of the third ventricle 
as far back as the superior commissure (fig. 2, s.c.) is deeply 
invaginated to form a complex choroidal fold (fig. 2, ch. 3; also 
figs. 9—15), which later on forms the “ diaplexus” of Wilder. 
It is evident, therefore, that no Zirbelpolster of Edinger (par- 
encephalon, prepinealis Zwischenhirndach) exists in this brain, 
since the velum or origin of the median plexus extends right 
back to the superior commissure. The latter is a very small 
band of transverse fibres connecting the two ganglia habenule. 
Immediately behind the superior commissure is the epiphysis 
cerebri, which consists of a small solid clump of cells (fig. 2, 
ep.) with deeply stained nuclei, lying behind a small recessus 
pinealis and upon the posterior commissure (p.c¢.). The latter 
is a broad band of transverse fibres, and is new generally re- 
cognised as the limit of the diencephalon. 
The constricted anterior pole of each hemisphere is distin- 
guished as an olfactory bulb by the application of the olfac- 
tory ganglion to its periphery (figs. 18 and 4, olf. g., J.g.). 
