. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. ENCEPHALON OF FISHES. 283. Brain of Shark, CarcharUis example, is elongated in the axis of tlie skull, and is of a sub- ccimpressed oval form, and has a large ' lateral ventricle' in its interior in the Lciiidosiren, fig. 186, I v. In the Skate, tlie pros- encephala coalesce into a subdepressed transversely elongated mass, their essential distinction Ijeing indicated by a mere super- ficial median fissure ; in Carcharias, fig. 187, the jjrosencephalon forms an almost ghjbular mass, with scarcely a trace of a median fissu
. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. ENCEPHALON OF FISHES. 283. Brain of Shark, CarcharUis example, is elongated in the axis of tlie skull, and is of a sub- ccimpressed oval form, and has a large ' lateral ventricle' in its interior in the Lciiidosiren, fig. 186, I v. In the Skate, tlie pros- encephala coalesce into a subdepressed transversely elongated mass, their essential distinction Ijeing indicated by a mere super- ficial median fissure ; in Carcharias, fig. 187, the jjrosencephalon forms an almost ghjbular mass, with scarcely a trace of a median fissure. Amouo- Ijony fishes the ^ -' 187 lirosencephalic lobes are more or less confluent in Luciuperca Sdiidrti, Tracliimis draco, S//r- f/us, Mullus, Scomher trachiims, Belone, Cliipea harengus, and Chipea sprruttus; they appear distinct symmetrical spheroids in most other fishes, their union being reduced to a small trans- verse medullary band (iirosencephalic commissure).' The sym- metrical character of the prosencephala, as of the optic lobes, is Avanting in most Pleuronectida. The grey vascular neurine forms the greatest part of tlie pros- encephalon inmost Osseous Fishes; the white fibres radiate through this, and rarely appear on any part of the exterior surface; the white substance, however, predominates in the Plagiostomcs and Lepidosiren. As a rule, the proseneephalic lobes are solid; but the l^rain of Carcharias ^ shows a deep ventricular fissure at the anterior and under part of the prosencephalon, with a vascular fold of membrane or ' choroid plexus' penetrating the fissure, wdiich is continued forward into the orus of the olfactory lobe. The lateral ventricle is more extensive in the Lepidosiren, and is continued directly into the olfactory lobe. The ' rhinencephalon ' figs. 173—176, R, consists of two always distinct lobes of grey matter, which receive the prolongations of chiefly white fibres from the prosencephalon and its crura, and give off the nerves to the o
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