PLATE 3 
EXPLANATION OF FIGURES 
8 Ventral view of head of Mustelus (probably vulgaris). > 1. 
9 The same, dissected so as to show the ala nasalis on left hand side of figure, 
and the nasal pit on right hand side. X 1. 
10 Ventral (external) view of left ala nasalis of Mustelus. X 2. 
11 Dorsal (internal) view of the same. X 2. 
12 Lateral view of the head of Ceratodus forsteri. X 1. 
i) 
S 
bo 
