490 J. B. JOHNSTON 



form lobe, corjius striatum and pallium in the turtle are readily 

 comparable with those in the manunal, the identification of 

 the lateral zona limitans in the turtle completes the history of 

 this important landmark throughout the series of vertebrates. 

 The boundary lines between the pallial and basal portions of 

 the hemisphere are now clear in both medial and lateral walls 

 in fishes, amphibians, reptiles and mammals (Johnston, '11a, 

 '13 b, '15 b). 



The relation of the dorsal ventricular ridge to the amyg- 

 daloid complex requires further comparative study. In the 

 adult, it will be remembered, the caudal part of this ridge is 

 separated from the rest by a broad shallow groove which con- 

 tinues in the general direction of the deep middle ventricular 

 groove ('15 b, figs. 4 and 10). This caudal portion of the ridge 

 is made up of the medial amygdaloid nucleus and of an apparent 

 infolding of the general pallium. Even in the oldest of these 

 embryos the dorsal ventricular ridge extends into the tip of 

 the caudal pole as a simple thickening of the general pallium. 

 It seems probable, although the evidence is not sufficient for 

 a definite conclusion, that the caudal portion of the ridge in- 

 cluding the large-celled medial amygdaloid nucleus is formed 

 from this thickening of general pallium. 



For the photographs of the models I am indebted to Dr. W. F. 

 Allen of the University of Oregon. 



LITERATURE CITED 



Johnston, J. B. 1911 a The telencephalon of selachians. Jour. Comp. Neur., 

 vol. 21. 



1913 b The morphology of the septum, hippocampus, and pallial 

 commissures in reptiles and mammals. Jour. Comp. Neur., vol. 23. 

 1915 b The cell masses in the forebrain of the turtle, Cistudo Carolina. 

 Jour. Comp. Neur., vol. 25. 



