of the Anatomy of the Squalus Maximus. 231 



of the brain of a Squalus Acanthias, (PL XXI.) that the two 

 may be compared together, with a view to shew the relative 

 size of the parts, one belonging to a shark of thirty feet, the 

 other to one of three feet long. 



In the brains of what we consider the animals of greatest 

 intelligence, there is a cerebrum, cerebellum, and medulla 

 oblongata ; beneath the cerebrum there are the tubercula qua- 

 drigemina. In fishes, the cerebrum is wanting, and there is 

 no part at all analogous to it, unless we consider the enlarge- 

 ments, from which the olfactory nerves arise, to be of that 

 description. 



These enlargements are separated from the other parts of 

 the brain by the optic nerves going off in a transverse line 

 between them and the tubercula quadrigemina. In the pre- 

 sent specimen, unfortunately, not only the enlargements from 

 which the olfactory nerves go off, were destroyed ; but also a 

 portion of each of the anterior tubercula quadrigemina: the 

 cerebellum was, however, entire, and is represented of the 

 natural size. 



The brain does not occupy more than one-third of the cra- 

 nium. The medulla spinalis is large in proportion to the brain. 

 From the termination of what corresponds to the calamus 

 scriptorius in the human brain, a fissure extends on the upper 

 part of the medulla spinalis, dividing it longitudinally into 

 two portions ; there is a similar fissure on the anterior sur- 

 face ; into both of these a thin fold of pia mater extends and 

 adheres with firmness to the surfaces with which it comes in 

 contact. 



The dura mater is very dense, and adheres firmly to the 

 inner surface of the cranium and theca vertebralis. The pia 



