830 



The Brain of the Archccoceti. 



[Jan. 15, 



the [basal] region, and perhaps of the whole brain, is the great depth 

 of the ectorhinal fissure, a feature marking off the present form very 

 strongly from DelpMnus " (p. 438). Since his illustrations do not 

 properly delineate this interesting conformation, Professor Haswell 

 kindly permitted me to examine his specimen ; and Mr. J. P. Hill has 

 made me an excellent photograph (of its ventral surface), roughly 

 reproduced in the accompanying drawing (fig. 4). It shows the com- 

 plete and quite-typical rhinal fissure and the characteristic pyriform 

 lobe. In its anterior part the rhinal fissure is fully a centimetre deep. 



Fid. 4. — Ventral aspect of left hemisphere of Cogia Gregi. Kedueed approxi- 

 mately one-half, a.d., corpus striatum (desert region) ; b.o., place occupied 

 by bulbas olfactorius in foetus ; f.r.a., fissura rhinalis anterior ; f.r.p., fissura 

 rhinalis posterior; l.b. y lobus pyriformis. 



The exact reproduction of these characters of the rhinencephalon in 

 an adult anosmatic Cetacean, and the presence of the olfactory bulb in I 

 the foetal Narwhal, show that these toothed Cetaceans were certainly 

 (and probably quite recently) derived from ancestors presenting the 

 normal mammalian t}^pe of olfactory apparatus. The absence of the 

 olfactory bulb and peduncle in the Odontoceti cannot, therefore, be 

 considered a just reason for adopting the utterly-improbable suggestion 

 of a nearer affinity of the Archasoceti to the Mystacoceti than to the 

 Odontoceti. 



Estimated by the amount of sand which it displaced, the bulk of the 

 natural cast (including that of a considerable quantity of matrix 

 attached to the base of the brain and some small fragments of bone) 



