THE WHALE BIRD. 105 
MATERIAL IN THE ‘ DiscoveRyY’s’ COLLECTION. 
No. 126, ad. sk., 6. Oct. 22,1901. Atsea. 45°S. 40° 57' B. 
The colouring of the soft parts :— 
Upper bill, pale bluish 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. 
Tris, 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 would otherwise be possible. Darwin, in his “ Origin of 
Species,” makes the following remark: “In the genus Prion the upper mandible alone 
is furnished with lamelle, 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 lamelle 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 (8). 
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. 
