324 PHILOSOPHICAL TRANSACTIONS, [aNNO 1787» 



of the length of the jaw. The head in my possession is 1 9 feet long, the semi- 

 diameter not quite 5 feet : if this proportion is preserved, those whales which 

 have whalebone 15 feet long must be of an immense size. These plates are 

 placed in several rows, encompassing the outer skirts of the upper jaw, similar 

 to teeth in other animals. They stand parallel to each other, having one edge 

 towards the circumference of the mouth, the other towards the centre or cavity. 

 They are placed near together in the piked whale, not being ^ of an inch 

 asunder where at the greatest distance, yet differing in this respect in different 

 parts of the same mouth ; but in the great whale the distances are more 

 considerable. 



The outer row is composed of the longest plates ; and these are in proportion 

 to the different distances between the 2 jaws, some being 14 or 15 feet long, 

 and 12 or 15 inches broad ; but towards the anterior and posterior part of the 

 mouth, they are very short : they rise for half a foot or more, nearly of equal 

 breadths, and afterwards shelve off from their inner side, till they come near to 

 a point at the outer : the exterior of the inner rows are the longest, correspond- 

 ing to the termination of the declivity of the outer, and become shorter and 

 shorter till they hardly rise above the gum. The inner rows are closer than the 

 outer, and rise almost perpendicularly from the gum, being longitudinally 

 straight, and have less of the declivity than the outer. The plates of the outer 

 row laterally are not quite flat, but make a serpentine line, more especially in 

 the piked whale the outer edge is thicker than the inner. All round the line 

 made by their outer edges, runs a small white bead, which is formed along with 

 the whalebone, and wears down with it. The smaller plates are nearly of an 

 equal thickness on both edges. In all of them, the termination is in a kind of 

 hair, as if the plate was split into innumerable small parts, the exterior being 

 the longest and strongest. 



The 2 sides of the mouth composed of these 2 rows meet nearly in a point at 

 the tip of the jaw, and spread or recede laterally from each other, as they pass 

 back ; and at their posterior ends, in the piked whale, they make a sweep in- 

 wards, and come very near each other, just before the opening oesophagus. In 

 the piked whale there were above 300 in the outer rows on each side of the 

 mouth. Each layer terminates in an oblique surface, which obliquity inclines 

 to the roof of the mouth, answering to the gradual diminution of their length; 

 so that the whole surface, composed of these terminations, forms one plane 

 rising gradually from the roof of the mouth ; from this obliquity of the edge of 

 the outer row, we may in some measure judge of the extent of the whole base, 

 but not exactly, as it makes a hollow curve, which increases the base. The 

 whole surface resembles the skin of an animal covered with strong hair, under 

 which surface the tongue must immediately lie, when the mouth is shut ; it is of 

 a light brown colour in the piked whale, and is darker in the large whale. 



