193 
EXPLANATORY NOTE. 
An examination of a large quantity of fresh Monotreme- 
material since this paper was written has convinced me that 
undue importance has been attached to the degree of flexion as an 
index of a Monotreme cerebrum. Thus in Ornithorhynchus the 
hippocampus possesses quite an extensive descending limb. It is, 
however, of a very diminutive size, and in all my earlier speci- 
mens had become knocked off in preparation for cutting. It is 
so small, however, and its fimbria so insignificant that it may be 
neglected in discussing the morphology of the hippocampal com- 
missure. In Zchina also, the descending limb is much more 
extensive than my earlier examinations lead me to believe. 
In my paper on the Platypus brain, which I expect to publish 
soon, the bearing of these facts will be fully discussed. 
