466 CETACEA. 



I have hitherto said little respecting the lobes, these being, in fact, very much out 

 of position compared with the mould of the brain. A frontal, parietal, occipital 

 and temporal are undoubtedly present and well marked, but regarding the so-named 

 middle or central lobe of Gratiolet I hesitate to affirm anything. 



On making a median longitudinal section of the brain, and thus exposing the 

 inner cerebral face, I noted among others the following points : the great and pre- 

 ponderant volume of the occipital lobe; the very considerable depth of cerebral 

 substance above the corpus callosum, &c. ; an unusual arching of the corpus 

 callosum of moderate thickness at its middle, but with greatly increased thickness 

 of the anterior genu, and specially knob-like posterior spherical extremity ; some 

 depth of the fornix behind, but thinning forwards ; the thalamus opticus of 

 relatively small, or rather moderate dimension ; and prominent corpora quadri- 

 gemina. 



As to the convolutions and sulci of this inner face, the callosal gyrus makes 

 one great sweep from behind forwards, broadening as it proceeds, and at its sharp 

 turn in front being twice as wide as it is behind. It has no folds in its entire 

 course. The calloso-marginal gyrus is like the last and surrounds it ; having only 

 one oblique antero-posterior indentation at the frontal region where it is, so to 

 say, cleft. 



The lateral ventricles are short. The termination of the anterior cornu is 

 blunt and barely directed outwards, but, on the contrary, the cavity trends inwards 

 and is deep ; the corpus striatum being large, and markedly vertically directed. The 

 posterior cornu likewise is abbreviated so far as its sweep back and inward bend 

 extend, but it is nevertheless deep, and there is a rudimentary hippocampus minor, 

 agreeing with the small calcarine gyrus of the inner cerebral face. The middle 

 cornu also strikes very nearly straight downwards, and it possesses a distinct 

 hippocampus major. 



Views of the third and fourth ventricles were but imperfectly seen owing to 

 the above sections destroying the relations of the parts. 



The cerebellum is of considerable volume proportionally to the cerebrum, 

 although, all in all, less than obtains in Orcella. Its superior vermiform process 

 is narrow, not very prominent, but distinct. Lateral lobes are well marked, but the 

 flocculus is only of medium size. 



The pons Varolii {Fv) is short in both diameters, but it is thickish. As pre- 

 viously stated, corpora trapezoidea are attached to the medulla oblongata ; the latter 

 has no very marked columns, but its smoothness inferiorly may have been produced 

 by the spirituous medium in which it was preserved. 



The grey matter both of the cerebrum and cerebellum is proportionately in a 

 thick layer, and the sulci, as a rule, in both, are relatively deep. 



Lastly, I would note that the vascular supply to the brain must be great if 

 we judge by the membranes within and at its base. 



All things considered, the brain of Flatanista is wanting in the broad rotund- 

 ity of the Whale group generally and so marked in Orcella. To a very limited 



