190 RALPH EDWARD SHELDON 
structure and fiber connections (figs. 2 and 3). The deepest of 
these is the sulcus ypsiliformis, which arises from the ventro- 
lateral border about three-fourths of the distance back from 
the rostral pole of the basal lobe, ascends to the dorsal surface and 
here divides into an anterior and a posterior limb, which enclose 
a central eminence. This eminence contains the palaeostriatum 
and the primordium hippocampi, the latter covering the dorsal 
surface of the palaeostriatum, especially on its mesal border. 
The posterior limb separates the posterior pole from the rest of the 
hemisphere; the anterior limb separates the central eminence from 
the tuberculum anterius and the tuberculum laterale, these com- 
prising a part of the nucleus olfactorius lateralis. The remainder 
of the lateral olfactory nucleus is the nucleus pyriformis of the 
posterior pole. 
The anterior limb of the sulcus ypsiliformis corresponds fairly 
closely with the sulcus palaeopallio-epistriaticus of Thynnus and 
the fovea endorhinalis interna of Amia, as described by Kappers 
and Theunissen (08). 
On the mesal aspect of each basal lobe, extending for almost the 
whole length of the lobe is a well defined sulcus of great morpho- 
logical importance which has been ignored by other writers on 
the brains of fishes. It forms the dorsal boundary of the precom- 
missural body and has some points of resemblance with the fis- 
sura limitans hippocampi (C. Judson Herrick, ’10) in Amphibia 
and Reptilia, the fovea septocorticalis (Kappers and Theunis- 
sen) in Rana, and the fissura arcuata of Gaupp, with which, how- 
ever, it is not fully homologous, as will appear beyond. It will 
be designated sulcus limitans telencephali. 
Ventrally of this furrow lies the corpus precommissurale, termed 
the epistriatum by Kappers (’06), the lobus olfactorius posterior, 
pars medialis, by Goldstein, ete. 
An examination of fig. 4 shows that the fissura endorhinalis 
on the ventral surface of the hemispheres forms an open V._ It 
first appears rostrally at the point where the olfactory tract joins 
the hemispheres (fig. 24), gradually extending laterally until the 
base of the sulcus ypsiliformis is reached, whence it turns medially 
again. For the whole of its extent the tractus olfactorius lateralis 
