492 



J. B. JOHNSTON 



Fig. 1 Chelydra serpentina. The size of this embryo is indicated by the 

 owner by the words '8.5 mm. carapace.' Lateral view of a model of the right 

 hemisphere. Description in the text. 



This and the following models have been merely rubbed with a blunt instru- 

 ment to smooth the surface. The external surface has been painted so that the 

 olfactory centers and hippocampus appear dark and the general pallium light. 

 The diencephalon has been left with the gray color of the modelling paper and 

 the ventricular surface of the hemisphere has had no treatment whatever. The 

 lamina terminalis and line of attachment of the choroid plexus have been painted 

 white. All the models were made at a magnification of 50 diameters and are 

 reduced one-third in reproduction 



