NERVOUS SYSTEM. VERTEBRA TA. 87 



lateral line. In front of the lobus linete lateralis the 

 margins of the rhomboid fossa bend upwards and slightly 

 outwards to form the posterior crura of the cerebellum. 

 The cerebellum forms an upstanding recurved anterior 

 border to the rhomboid fossa. Its anterior parts (not 

 shown in the specimen) project within the optic lobes, 

 forming a valvula cerebelli as in Teleosts. Molecular, 

 nuclear, and intermediate layers are present in the cere- 

 bellum, but, as in Elasmobranchs, the distribution of the 

 nuclear layer is very partial, and Purkinje's cells are 

 irregularly disposed. The optic lobes are very small and, 

 as in Dipnoi and Urodeles, form a single globular enlarge- 

 ment without a distinct median furrow. They are said to 

 contain small tori longitudinales and semicirculares similar 

 to those of Teleosts. 



The thalamencephalon is narrow and fairly long, with a 

 well-developed hypothalamus. The sides of the infundi- 

 bulum are swollen to form a pair of small lobi inferiores. 

 The saccus vasculosus is well-developed. As in most 

 Elasmobranchs and many Teleostea, the epiphysis is long 

 and thread-like ; towards its base it is in close contact with 

 the roof of a large conical paraphysis. The cerebrum is of 

 relatively small size, and consists of basal ganglia (striatum 

 and epistriatum) covered by an epithelial roof, in which a 

 few nerve-elements have been observed. The olfactory 

 bulbs are sessile on the cerebrum ; each contains a cavity 

 in connection with the cerebral ventricle, and receives a 

 large olfactory nerve indistinctly separable into two bundles. 



Johnstone, Zool. Jahrb., Bd. xv. 1901, p. 59. 



TELEOSTEA. 



BablRuckhard, Arch. Anat. u. Phys. 1898, p. 345 (Pallium). 

 Haller, Morph. Jahrb., Bd. xxvi. 1898, p. 632 (Histol, 

 Bibliogr.}. 



The brain of Bony Fishes differs from that of Elasmobranchs 

 in many important features. It is far more concentrated longi- 

 tudinally, and is remarkable for the strong development of 

 the optic lobes, which in some cases completely dominate the 

 rest of the brain and render it nearly globular in form. On 



