Article IX-.—Some Notes on the Brain and Pineal Struo- 

 tares of Polyodon folium. By H. Gakman, Lexing- 

 ton, Ky. 



Some time about 1888 the writer of these notes made 

 several dissections of the bi-ain of this interesting" fish 

 and drawings of them were made by Magnus Westergren, 

 at that time Artist of the Illinois State Laboratory of 

 Natural History. Other duties have until recently pre- 

 vented further prosecution of the study, but I have 

 now to present some of the results of a reexamination 

 of these dissections, kindly placed in my hands by Pro- 

 fessor Forbes, together with some facts gained by a 

 study of fresh material obtained by me from the Ohio 

 River. For purposes of comparison I have dissected out 

 the brain of our common sturgeon {Acipenser rubicun- 

 dus). 



As in other sturgeons, the brain of Polyodon folium is 

 enclosed by a thick cartilaginous cranium. It rests on 

 the floor of a cavity which it only partly fills, the space 

 above being partly occupied by fatty tissue, but that 

 part dorsal to the mid-brain being almost entirely 

 empt^'. As if to make up for the deficiency of padding 

 about the brain, the fore- and mid- brains are enclosed 

 in a tough whitish fatty tissue of considerable thick- 

 ness, which can only be removed by the exercise of great 

 care, so closely and tenaciously does it adhere. A 

 peculiar feature of the brain when first exposed is a 

 dense black fat which encloses the hind-brain and fills a 

 large space surrounding the base of the spinal cord 

 where it leaves the medulla. I have seen nothing just 

 like it in other fresh-water fishes. 



The olfactory nerves are very large, indicating that 

 the sense of smell is an important one to the shovel- 

 "^sh. Each nerve is separated, from its origin on the 



