The Bram of Diemydylus Viridescens 299 



types. The sulci upon its endymal surface are compared 

 with those of diemyctylus. The pallium is considered as a 

 plexus much stretched, not an undeveloped part representing 

 the dorsal and mesal walls of other brains. 



9. Arguments and facts are given for considering the rhin- 

 encephal as equal to other segments having a tripartite 

 arrangement. 



This investigation has been carried on in the Anatomical 

 Laboratory of Cornell University where material and appli- 

 ances were most generously placed at my disposal. To the 

 writings of Dr. Wilder many references have been made but 

 to his lectures especially am I indebted for the full discussion 

 of morphological problems and especially of the difficulties 

 involved, 



Ithaca, N. Y., 

 Aug. 19, 1893. 



