394 J. B. JOHNSTON 
n.h 
28 29 I i I AME Ad 
Fig. 28 A diagram to show the disposition of the velum transversum. The 
outline is taken from figure 7, showing the dorsal aspect of the model of the Lam- 
petra brain. The tela chorioidea is drawn as it would appear if the epiphysis and 
parapineal body were removed. The velum transversum is drawn as a fold of the 
tela. 
Fig. 29 Professor Herrick’s figure 73 reprinted for comparison with figures 6 
and 9 of this paper. The figure is ‘‘a diagram reconstructed from actual sections * 
of the cyclostome brain, Ichthyomyzon concolor.” 
