500 PROSENCEPHALON OF SPINAX AS A TYPE OF ELASMOBRANCH FORE-BRAIN. 
EXPLANATION OF PLATES. 
Fig. 1. The brain of Spinax from the dorsal surface. 
Fig. 2. Transverse section of the left side of the anterior end of the prosencephalon, passing through 
the peduncle and its canal. 
Figs. 3 and 4. Transverse sections of the prosencephalon further posteriorly showing the areas 
of neurones. 
Figs. 5-12. Transverse sections showing parts of most of the fibre tracts described in the text. 
REFERENCE LETTERS. 
a corpus striatum 
ant. com. . . . anterior commissure. 
ant. pall. c. . . anterior pallial commissure. 
b tuberculum olfactorium. 
c formatio pallialis. 
d primordium hippocampi. 
dec. tr. olf. lat. . decussation of lateral olfactory 
tract. 
dor dorsal side. 
e paraterminal body. 
int.for. . . . interventricular foramen. 
lat. ar. 1, 2, 3 . lateral area with three sub-areas. 
lat. ven. . . . lateral ventricle. 
med.f. br. bun. . medial fore-brain bundle. 
nuc. hab. . . . nucleus habenulae. 
olf. ped. . . . olfactory peduncle. 
o. n optic nerve. 
p. o.r. . . . pre-optic recess. 
post. pall. c. . . posterior pallial commissure. 
pr', pr" . . . sulcus limitans lateralis, sulcus 
limitans medialis. 
r. . ' . . recess. 
str. med. . . . stria medullaris. 
sul. Mon. . . . sulcus Mqnroi. 
thal. gr. . thalamic gray. 
tr. cort.-med. . . tractus cortico-medialis. 
tr. hipp. . . . tractus (commissura) hippocampi. 
tr. med.. . . . tractus medianus. 
tr. olf.-cort. lat. . tractus olfacto-corticalis lateralis. 
tr. olf.-cort. m.-c. tractus olfacto - corticalis medio- 
cruciatus. 
tr. olf.-cort. m.-d. tractus olfacto - corticalis medio- 
dorsalis. 
tr. olf .-hyp. lat. . tractus olfacto - hypothalamicus 
lateralis. 
tr. olf. -hyp. med. tractus olfacto - hypothalamicus 
medialis. 
tr. olf. lat. . . tractus olfactorius lateralis. 
tr. pall. . . . tractus pallii. 
tr. teen. . . tractus taeniae. 
tr. thal.-cort. . tractus thalamo-corticalis. 
v. tr. ... velum transversum. 
x , sc" zona limitans lateralis, zona 
limitans medialis. 
