ANATIDAE. 



Indeed, the examination which I made of the shells of the species 

 which come into consideration here, brought the following parti- 

 culars respecting the pigmentation to light: 



TADORNA TADORNA (L.). 



The chalk shell underlying the cream coloured glutinous layer is 

 white to the inner membrane. 



SPATULA CLYPEATA (L.). 



Greenish: the chalk shell underlying the glutinous layer is coloured 

 bluish green at the surface; the intensity of colour diminishing 

 gradually towards the inner membrane. 



Yellowish: the chalk shell underlying the glutinous layer \s cream 

 coloured to the inner membrane. 



ANAS BOSCHAS L. 



Greenish: the chalk shell underlying the glutinous layer is coloured 

 bluish green at the surface, gradually changing into sea green to the 

 inner membrane. 



Yellowish or brownish yellow: the glutinous layer is coloured dirty 

 yellow or brownish yellow; the immediately underlying chalk layer 

 is coloured bluish green, and the fundamental layer (superposed on 

 the inner membrane) is coloured sea green; between the two lies 

 a layer of a deep cream colour. 



Whitish: in this shell oocyanin is absent from the chalk pigment- 

 layer immediately underlying the glutinous layer, or it occurs therein 

 in so slight a quantity as not to show through on the outside. 



