82 PHYSIOLOGICAL SERIES. 



saocus vasculosus, and hypophysis are also strongly 

 marked. The latter is connected (as in other Elasmo- 

 branchs) by a blood-vessel to a transverse bar of vascular 

 connective tissue closely adherent to the perichondrium. 

 The cerebellum differs from that of a Shark in the slight 

 development of its anterior lobe. Its surface is smooth 

 except for a single transverse furrow and slight lateral 

 indentations. At the sides of the posterior lobe lie the 

 wrongly developed auricles and lobi lineas lateralis ; the 

 latter apparently owe their size to the peculiarly large nerve- 

 supply necessary for the lateral-line organs and ampulla?. 



The medulla shows a very high degree of antero-posterior 

 concentration, the rhomboid fossa extending only a short 

 way beyond the cerebellum. 



D. 83. The brain of a Skate (Raja batis) dissected to show its 

 internal structure. The dorsal parts of the cerebrum have 

 been removed to show the solidity of its walls and the 

 extremely small size of the ventricle. The latter, although 

 of some little extent in the horizontal plane, is reduced to 



Fig. 22. 



OPT.N 



robrum of Raja batis (horizontal section). 



N -lit dorso-vent rally. Its outline can be traced with 

 difficulty in the -j.eciinen ; it is clearest towards the 



mities (if the lateral ventricles. 



1'.- hind the cerel.nnn, the brain has been divided by a 

 mid-sagittal inei-ion and its two halves have been separated. 

 Its internal structure differs in several particulars from 



