416 NILS HOLMGREN 
forwards in the shape of a short cornet. ‘This cornet is laterally 
compressed between the hemispheres. Its opening is very wide 
(fig. 26), situated just at the level of the foramen monroi. From 
near the tip of the cornet its dorsal wall is folded into a chorioidal 
fold (ch.f.) hanging down in the cornet and extending backwards 
in the epithelial roof of the forebrain as the medial chorioidal 
fold mentioned above. From the form and the height of the 
recessus neuroporicus it results that the ependymal tela of the 
forebrain in the pallial region is not fastened at the medial border 
of the inverted pallium (fig. 28), but some distance dorsal or 
lateral to this border, a point of attachment peculiar to Chimaera. 
In the pallium there are two layers of nerve-cells present, a 
ventricular and a more distal one. The distalis not very distinct 
(figs. 24, 25, 27), mostly consisting of scattered cells, sometimes 
ageregated to form a sort of cell-lamina (fig. 24), sometimes co- 
alescing with the ventricular layer (fig. 26). It is thus impossible 
to say whether there is really a regular cortical layer present; 
probably there is one, but studies on embryonic material are 
necessary for stating this. I have no such material. 
The subpallial parts are very strongly developed. The lateral 
olfactory nucleus (n.olf.l.) is very large, covering most of the 
lateral surface of the forebrain. ‘The lateral brain-wall is very 
thick and, a little before the level of the foramen monroi, pro- 
jects a little into the ventricle, forming a swelling which perhaps 
may be considered as a ‘corpus striatum’ (st.s.). In this swelling 
is found a condensation of nerve-cells corresponding to the so- 
called ‘epistriatum’ in sharks. But this ‘epistriatum’ is sub- 
pallial, and thus not homologous with the ‘epistriatum’ in 
reptiles and birds, where it is pallial (hypopallium of Elliot 
Smith), situated dorsal to the zona limitans lateralis. Farther 
back from the foramen monroi the lateral wall of the ventricle 
exhibits another similar swelling (fig. 28, st.s.2) of very great 
distinctness. These two ‘striatal’ swellings surely are homolo- 
gous with those of Acanthias. But as they have no special charac- 
teristics allying them with the ‘striatum’ of reptiles, I am not 
quite disposed to ascribe to them the value of a corpus striatum. 
4 Perhaps, however, they correspond to a real striatum, but there are no 
special reasons for accepting this view. 
