ft 



c b a 



FIG. 2. Shows the skulls of Mus norvegicus (a), albino rat (/;) and Mus ratlus (t). The skulls were 



photographed from two different aspects, in order to show various views of the skulls for a comparison. 



The upper row was taken from the dorsal aspect, and the lower from the ventral. The figures are about 

 the natural size. 



