THE WHALE BIRD. 105 



Material in the ' Discovery's ' Collection. 

 No. 126, ad. sk., ^ . Oct. 22, 1901. At sea. 45" S. 40° 57' E. 



The colouring of the soft parts : — 



Upper bill, pale bluisli grey, shading into black at the base and on the nostrils, the 



central part of the culmen also black and the terminal part or point of the upper 



bill yellow. 

 Mandible, pale blue, with a black line along the centre of each side, and the tip black. 

 Iris, dark brown. 

 Legs and toes, pale blue. 

 Webs, flesh pink, with the free borders grey. 

 Nails, grey. 



Material in the 'Morning's' Collection. 

 No. 1, ad. sk. Nov. 25, 1902. 



The various species of Prion are not readily distinguishable upon the wing, so that 

 observations made on board ship and from a distance only are open to a very 

 considerable amount of doubt. Prion vittatus, however, can occasionally be certified 

 at close quarters by the enormous width of the upper bill. We obtained one or two 

 specimens on the ' Discovery,' and were much interested to find that the floor of the 

 mouth was very extensile, enabling it to take up a much larger quantity of water 

 and small crustaceans than wouLl otherwise be possible. Darwin, in his " Origin of 

 Species," makes the following remark : " In the genus Prion the upper mandible alone 

 is furnished with lamellae, which are well developed and project beneath the margin ; 

 so that the beak of this bird resembles in this respect the mouth of a whale." If the 

 lower bill of a dried skin is examined more than this would hardly be noticed ; for the 

 loose blue skin between the rami of the lower jaw will be found dry and folded to 

 form a hard level floor to the mouth. But if the tip of the little finger is inserted 

 into the mouth of a freshly killed specimen, it will be found that the neatly folded 

 skin can be quite easily distended into the form of a bag, or sac, something like that 

 of the pelican, which is obviously of use to a bird that has developed lamellae on 

 the upper bill which act like the baleen plates of a whale. The tongue is bright 

 orange-pink in colour, smooth and fleshy, and of a suitable muscular character to assist 

 in expelling the fluid from a mouthful of minute crustaceans and the water in which 

 they were taken up. The accompanying figures were made from a fresh specimen ; 

 in Fig. 45 (2), p. 104, the sac is lightly distended with a loose piece of cotton wool ; 

 Fig. 45 (1), .shows the sac in a state of normal contraction, and the neat small folds 

 into which it is then thrown are shown in Fig. 45 (3). 



The flight of the Prion petrels is wonderfully strong and untiring for such small 

 birds. They are apparently always on the wing, and one rarely sees them resting on 

 the water ; their flight is always very rapid, with quick changes, which show alternately 

 the wholly white underparts and underwings, and the blue-grey backs with the darker 

 V-shaped mark, which characterises this and allied forms of petrel. 



