358 ELIZABETH CAROLINE CROSBY 
the cortex of the pyriform lobe. The rhinal fissure is demon- 
strable in some of the material but is relatively slight. 
In the anterior end of the dorso-lateral area of the hemisphere 
there is a ridge of cortex-like cells which has the appearance of 
being a fold of the general cortex. This has been termed in the 
present paper, primordial general cortex. Between the primor- 
dial portion and the general cortex proper, at the medial border, 
there is a small space (fig. 6) which permits association fibers 
of the alveus system to reach the former portion. Johnston 
(15) has described in turtles a ridge of cells similar to the pri- 
mordial general cortex of this description. He calls it the dorsal 
ventricular ridge but says that it belongs to the general pallial 
complex (the general cortex of this description). In a later 
paper (’16) he shows that both the ridge and the general cortex 
are derived during embryonic development from the dorso- 
lateral area. Phylogenetically the general cortex complex arose 
under the influence of at least two types of fibers. 1. The one 
type consists of fibers carrying impulses from the somatic centers 
of the diencephalon to the dorso-lateral area of the forebrain by 
way of the lateral forebrain bundle. 2. Into this dorso-lateral 
area association fibers from the hippocampal and pyriform lobe 
complexes also distribute. As these latter areas differentiated 
a higher type of integrated impulses was brought in and, within 
the dorso-lateral area, neurones exhibiting a cortex-like type 
of differentiation appear. In this way within the basal dorso- 
lateral area, a primordial general cortex is probably formed. 
What the factors were which caused this primordial cortex to 
become more superficial in position and to separate from the basal 
dorso-lateral area to take on a true cortical form, of course is 
not certainly known. Perhaps one cause lies in the neurobio- 
tatic influence of the association fibers, the neurones migrating 
out along their dendrites toward the source of their stimulation. 
The whole of the general cortex complex is a step toward the 
differentiation of a neopallial area. To be sure, this complex is 
still closely linked with cortical olfactory areas, but it has a rela- 
tively large somatic component and its connection with the basal 
somatic areas is intimate. As maintained by Elliot Smith and 
