MORPHOLOGY OF THE AVIAN BRAIN.(') 



( Coiitimied. ) 



C. H. Turner. 



Additional Remark upon the External Morphology of the 

 Epencephalon. — As has been remarked above, the most re- 

 markable characteristic of the avian brain is a tendency 

 towards great compactness. This tendency has left its stamp 

 upon the epencephalon. In addition to being wedged into 

 the caudal V of the hemispheres, (-) and to being trans- 

 versely convoluted, (') the epencephalon suffers a most note- 

 worthy modification. Its cephalo- ventral extremity projects 

 mesad into the cavity of the fourth ventricle, thus producing 

 the almost unique phenomenon of a portion of the epen- 

 cephalon being embraced by the metencephalon (Plate VII, 

 Fig. 3; Plate XIV, Fig. 10; Plate XV, Fig. 7; Plate XVIII, 

 Figs. 9, 10, 21). 



v.— HISTOLOGY OF THE EPENCEPHALON. 



Although in its external form the avian epencephalon 

 resembles one of the embryonic stages of the higher verte- 



1 A Correction.— Dr. R. W. Shufeldt has called my attention to an error that 

 occurs on page 56, lines 16 to 18. Those lines should read : " My notes upon these two 

 birds are based upon a study of sketches given in the United States Geological Survey, 

 J. W. Powell, Director; third aiinual report (1881-82), p. 56, Fig. 8, and p. 70, Fig 20 "' 



2 Supra, p. 41. 



3 Supra, p. 51. . . 



