498 Dr. F. W. Mott and Miss A. M. Kelley. [ Mar. 6, 
layer measuring about 0°2 mm., the pyramidal layer about 1 mm., and the 
polymorph layer about 0:7 mm. (vide fig. 7, Plate 15). The pyramidal cells are 
not closely packed, and incline to a longitudinal columnar arrangement. There 
are no really large pyramidal cells either above or below the granules, the 
largest measuring about 144 by 7m. A number of granules are scattered 
at the bottom of the pyramidal layer, but they hardly form a distinct layer. 
Frontal £.—This area is very poor in cells. Those of the pyramidal 
layer are more scanty than in other parts of the neopallium; the largest 
cells are still smaller than in “ Frontal A,” and the granules are still less 
prominent. 
Sensory Areas. 
Whereas the archipallium and the frontal and motor areas (except the 
cortex described under “Motor B”) have no definite line of granules, 
the cortex covering the posterior half of the hemisphere and the temporal 
lobe is characterised by a deep granule layer, which indicates a sensory type 
of cortex. 
This conspicuous layer of granules is seen throughout the whole area, but 
there are various other distinctions in different parts of it, and it has been 
subdivided accordingly into the temporal type, the post-central type, and 
the visual type. Although distinct variations seem to justify these sub- 
divisions it must be pointed out that the changes from one type to another 
in this region are gradual, and that therefore the boundaries can only 
be approximately given. Stellate cells are seen among the granules, but 
they are more numerous and more typical in the temporal and visual regions 
than in the post-central. 
Post-central Area : = 
Extent and Boundarives.—The post-central type of cortex lies on the dorsal 
and mesial surfaces, between the motor and visual areas. Anteriorly, about 
6 mm. behind the anterior extremity of the lateral sulcus it merges into an 
area intermediate to it and the motor area; and, posteriorly, near the 
posterior end of the lateral sulcus into one intermediate to it and the visual 
area. Inferiorly, on the dorsal surface, it extends across the lateral sulcus, 
where it merges into the temporal type, and on the mesial surface it extends 
to the limbic cortex. The change from the post-central to the temporal 
types is so gradual as to be scarcely perceptible, and it is only by comparing 
the upper part of the post-central with the temporal area that the 
differences in type become apparent. _ | 
Characteristics —The cortex is about 1°83 mm. in depth; the molecular 
