232 ALUS. [Vol. XVIII. 



The posterior halves of these swellings, in Scomber, are sep- 

 arated by a narrow fissure from the overlying hind end of the 

 cerebellum, the fissure extending transversely, in a curved direc- 

 tion, from one side of the brain to the other, and separating the 

 ventral surface of the hind end of the cerebellum from a narrow 

 bridge of nervous matter which bridges over the anterior portion 

 of the fourth ventricle. A similar bridge, said to be of gray mat- 

 ter, is said by Wright to connect the so-called tubercula acustica 

 in Amiurns, but his drawing of the brain of that fish seems to show 

 the bridge and the hind end of the cerebellum continuous, with- 

 out a separating fissure. The same is true of Herrick's drawings. 

 The bridge in Scomber is of variable thickness, being in some 

 specimens nearly as thick as the overlying part of the cerebellum, 

 and in others considerably thinner. It lies directly dorsal to a 

 second bridge of nervous matter which apparently represents the 

 lobi trigemini of Wright's descriptions, and the trigeminal tubers 

 or tuberosities of Herrick's. In Goronowitsch's descriptions of 

 Lota (No. 32) the bridge formed by the Cerabellarleisten seems 

 to correspond to this second bridge in Scomber. 



Immediately posterior to the bridge formed by the lobi trigemi- 

 ni, if they be such, are two other lobes, probably the lobi vagi. In 

 certain specimens they meet and touch in the medial line, but with- 

 out being fused. In others they are separated by a median cleft. 



Posterior to the lobi vagi there is a small swelling on each side, 

 marking the posterior limit of the fourth ventricle. 



The hypoaria are large and flat, and touch in the middle line 

 throughout the larger part of their length. Their general shape and 

 disposition is shown in Fig. 65. Anteriorly they diverge, leaving 

 a space in which is found the hypophysis, which is round in out- 

 line and usually with a bluntly pointed ventral end. No separate 

 saccus vasculosus was found in any of the several dissections 

 made. Whether it was removed in the dissecting, or formed part 

 of the so-called hypophysis, was not determined. 



2. Nervus Olfactorius. 

 The Nervus Olfactorius (0/) arises from the anterior end of 

 the lobus olfactorius, and runs at first almost directly forward in 

 that anterior extension of the cranial cavity that is enclosed in the 



