70 CETACEA. 



an elegant arched form. The 314 external or labial plates do not 

 extend to the whole extent in a transverse direction, but a system of 

 numerous small and narrow plates succeeds the external ones. For 

 each external jjlate, twelve (internal) smaller ones could be easily 

 counted ; so that the number of plates which could be counted, and 

 not including the bristly terminations towards the snout, phai-jnix, 

 and mesial line, stand thus : external or labial plates, 314 ; internal 

 small plates, corresponding to each external one, 12 : total number 

 of baleen plates, 3768. The longest plate of baleen is placed about 

 the centre of each of the sides, and measured 26 inches in length and 

 15 in breadth. The substance when recent is highly elastic and very 

 heavy ; the whole weighed nearly two tons. 



In Balcena minimus, Knox (Balcenoptera rostrata), 307 external 

 or labial plates (baleen) can be counted on each side ; towards each 

 extremity these plates degenerate into fine bristles, which were not 

 comited. The plates hang perfectly parallel with each other, and 

 from their closeness and fringed lingual aspect, must act as a very 

 perfect filter in collecting the minute molluscous animals, and at the 

 same time enable the whale to eject the water. 



The baleen or whalebone afi'ords good characters for the separation 

 of this family into sections. It is short or long accordiag to the 

 species of Whale, being modified entirely by the more or less arched 

 form of the upper jaw. Mr. Knox first pointed out this curious 

 and important fact. The usual conclusion come to by all persons 

 was, that the size of the whale corresponded to the length of the 

 bone or baleen. Now this is only good with regard to one species of 

 Whale, and not at all to the whole group of Whalebone Whales. — 

 Kno.v, Cat. Prej}. Whale, 8. 



The whalebone of the smooth -bodied Whales without any back-fins 

 (Balcena) is elongate, much longer than broad at the base, and gra- 

 dually attenuated, and edged with a fringe of equal, lengthened, fine, 

 soft bristles. The baleen is internally formed of a thin layer of fibres, 

 covered on each side with a thick coat of ' enamel' ; when dry and 

 out of the mouth, the blades are flat. 



The whalebone of the plaited-beUied Whale with a bunch {Mega- 

 ptera) or a dorsal fin {BaJanoptera) is short, broad, triangular, not 

 much longer than broad at the base, and rapidly attenuated, and is 

 edged with a series (sometimes rather crowded) of elongate, rigid, 

 imequal bristle-like fibres, which become much thicker and more 

 rigid near and at the tip. The baleen is internally formed of a more 

 or less thick layer of thick fibres, covered on each side with a thin 

 layer of enamel, and when dry and out of the palate they are curled 

 up and somewhat spirally twisted. 



The thickness of the plate of baleen depends on the number of 

 bristles. In the baleen oi BaJcna maximus there are 506 bristles in 

 the thickness of the plate, and by a rude enumeration there appeared 

 to be at least 130 bristles in each inch. The whole breadth of the 

 plate being 5^ inches, gives us 747 bristles entering into its compo- 

 sition. These bristles are matted together to the extent of 1 1 inches 

 on the external and 5 inches on the internal margins, by a substance 



