DEVONIAN FISHES OF IOWA 



267 



entirely new chapter, however, in the anatomy of extinct animals 

 is opened by the discovery of the actual phosphatized brain, 

 internal ear and blood vessels of a Palaeozoic vertebrate, such as 

 are clearly revealed by the contents of these fish-bearing nodules 

 from the base of the Waverly in Kentucky. 



Perhaps the best single specimen thus far examined which 

 displays the actual brain itself in situ, with parts of the audi- 

 tory sense organ on either side, is that shown in the accompany- 

 ing text-figure (Fig. 40 A, A 1 ). In the middle figure of the 



Fig. 40. Ehadinichthys deani, sp.nOY. Base of the "Waverly in Boyle county, Kentucky. 

 In tliis photograph are shown detached heads forming the central mass of phosphatic nod- 

 ules. The latter are split open in such manner as to cleave through the head longitudinally 

 immediately below the cranial roof, and exposing the fossilized organs of the brain:— the 

 olfactory lobe, cerebral hemispheres (covered in the central figure by a choroid plexus), 

 optic lobes, and cerebellum, on either side of which are to be seen the well preserved semi- 

 circular canals with their saccular and ampullae. Very nearly natural size. 



same illustration is seen the interior of the head of another 

 example which allows of the removal of the brain from its proper 

 cavity, thus facilitating its inspection from all sides. For the 

 purpose of photographing the organ more distinctly, it has been 

 placed in a right line above the head to which it belongs, and is 



