1903.] 



The Brain of the ArchceocetL 



325 



there is (in the natural cast) a large, irregular mass of a very peculiar 

 shape, not exactly comparable to the condition occurring in any other 

 brain known to me. 



Immediately behind the hemispheres (b) there is a great transverse 

 bar (c) measuring 125 mm. in the transverse direction — i.e., extending 

 on each side 15 mm. beyond the lateral margin of the cerebrum (b). 



Each lateral extremity of this mass (c) is expanded to form a large 

 buttress. In the natural cast these buttress-like masses are practically 



Fig. 2. — Dorsal aspect of the artificial cranial cast of Zeuglodon. § natural size. 

 a, b, c, d, as in fig. 1. a\ the dorsal rostrum, and b', an irregular boss on the 

 cerebral hemisphere. (These are probably due to imperfections in the 

 cranium.) 



vertical, and of uniform thickness ; whereas in the artificial cast they 

 are obliquely-placed, and expanded ventrally. In the natural cast the 

 mesial continuation of these thick lateral masses (each of which 

 measures 30 mm. antero-posteriorly) becomes reduced to a bridge 

 measuring only 5 or 6 mm. [the exact figure cannot be stated, because 

 a piece of bone (fig. 1, e) partially covers this region]. 



In the deep concavity behind the narrow bridge of the area c (in the 

 natural cast) two rounded, irregular, walnut-like bosses project, one on 

 each side of the middle line (fig. 1, d). Each of these is 26 mm. in 



2 A 2 



