Herri CK, Morpholoi^y of Brain of Bony PisJies. 233 



lanus, Cottus, Trigla, Amblyopsis, Echeneis, the Ganoidei 

 and Lepidosiien; and long-stalked in Salmo, Cyprinus, 

 Brama, Tinea, Gadus, Lota, Hippoglossus, Clupea, Belone, 

 Leucioperca, Cobitis, Plectognathi and Plagiostomi. 



The Cercbriiiii. — The topography of the cerebrum cannot 

 be satisfactorily discussed until much extended and careful 

 observations have been accumulated. In the groups examined 

 it is relatively constant, and such differences as appear are 

 often less important than they at first seem. The form varies 

 chiefly as a result of the varying size and position of adjacent 

 portions of the brain. The dorsal view^ usually presents a 

 sub-quadrangular outline, tending to oval. From the side 

 one may observe a rudimentary fissure and curvature corre- 

 sponding to the fissure of Sylvius of higher brains. The 

 transverse section is nearly always sub-triangular, with the 

 curved base of the triangle dorsad. The cerebrum presents 

 three well-marked aspects: a mesal surface, facing the median 

 fissure (in cases where the pallium of the tw^o hemispheres 

 fuses completely this aspect is absent or represented solely by 

 the corresponding aspect of the axial lobe); a dorsolateral 

 aspect, generally one continuous curved surface; and, third, a 

 ventral or rhinalic aspect. The last mentioned surface differs 

 from the others in being chiefly a non-cortical or axial 

 surface, as is the case in the corresponding area of higher 

 brains. It is bounded laterally by a more or less distinct 

 fissure or sinus, the rhinalis sinus, which is more distinct, 

 cephalad. This fissure is the undoubted homologue of the 

 rhinalis fissure of higher vertebrates in so much as the radix 

 lateralis of the olfactory crus occupies the adjacent region. 

 The pallium separates at this point. It must be constantly 

 kept in mind that the fissures upon the dorsal surface of the 

 cerebrum of fishes cannot have the same significance as the 

 cortical fissures of mammals. The Sylvian fissure, however, 

 seems to be obscurely indicated by a depression near the 

 middle of the lateral surface, which results from an incipient 

 flexture. There are iflpon the dorsal surface a number of de- 



