of the Anatomy of the Squalus Maxmus. 241 



a a. Cerebellum. 



bb. Two of the tubercula quadrigemina. 



c c. The part which corresponds with the fourth ventricle 

 in the human brain, surrounded by an oval, continued, nervous 

 band, from which the principal nerves go off. 



ddd. Portions of the three semicircular canals of the ear in 

 the cartilaginous cavity in which they are contained. 



Plate XXI. 



A view of the upper surface of the brain of the Squalus 

 Acanthias, taken from a fish three feet long, to shew the dif- 

 ference of appearance and size between it and that of the 

 Squalus Maximus. 



The brain is entire, and the eyes are left in their situation, 

 so that when this Plate is compared with that of the large 

 brain, the parts that are wanting in it will be readily distin- 

 guished. 



Plate XXII. 



A view of the heart of the Lophius Piscatorius in a distended 

 state, shewing the transparency of its coats, which are ex- 

 tremely thin. 



J. The auricle. 



b. The ventricle. 



c. The branchial artery. 



J. The projecting muscular tube serving as a valve. 



