144 Journal of Comparative Neurology. 



in Nectiuus than in the smaller urodeles^ above mentioned. 



The greatest widths are at the olfactory lobes and at the 

 caudal extremities of the cerebrum, at which points they are 

 approximately the same, and much greater than in the parts 

 farther caudad. The height (dorso-ventral diameter) does not 

 vary greatly in the different regions ; it is least in the region of 

 the oblongata and greatest through the infundibulum where the 

 height exceeds the width. 



On the dorsum, between the caudal portions of the cere- 

 brum, is the supraplexus enclosing the paraphysis. Caudad of 

 this and likewise between the caudal ends of the cerebrum, is the 

 diatela, bounded caudally by the habenas and at the meson by 

 the supracommissure. The epiphysis is almost circular in out- 

 line, lying dorsad of the supracommissure and extending caud- 

 ad to the postcommissure and also slightly cephalad. There 

 is no ectal distinction on the dorsum between the diencephal and 

 mesencephal save possibly a slight transverse furrow at the post- 

 commissure. 



Pigment is generally present on the mesencephal and ab- 

 sent from the diencephal, but this distinction is not constant, 

 the diencephal often being as highly pigmented as the mesen- 

 cephal. 



On the ventral surface is conspicuous the large hypophysis 

 attached to the caudal portion of the infundibulum. The optic 

 nerves are very small and the chiasma is not superficially notice- 

 able. Cephalad of this is a subtriangular space bounded by a 

 whitish area marking the region of the preoptic and lateral optic 

 recesses. The metencephal is simple and very long ; indeed, 

 it equals in length the entire remainder of the brain. It tapers 

 gradually from its widest point at the exit of the fifth nerve to 

 the myel. 



The cerebellum is represented only by a small transverse 



iThe restriction of Urodela and urodele by Cope to a single order of tailed 

 Amphibia is unfortunate; it leaves no convenient term that can be applied to all 

 the tailed Amphibia in contrast to the Anura or tailless forms, — a convenient 

 grouping, although perhaps not of taxonomic value. Urodele is used here as 

 synonymous with "tailed amphibia." 



