398 THE AKATOMT OF VEETEBRATED ANIMALS. 



and the space between the rami of the mandible is very 

 much greater than the width of the maxillo-premaxillary 

 part of the skull, which tapers to its anterior' end, and 

 is more or less convex upwards and concave inferiorly. 

 The two rami of the mandible are connected only by 

 ligament at the symj)hysis. 



Minute teeth are developed in foetal Balcenidoe, but are 

 very soon lost, and theii" place taken by the so-called Whale- 

 bone, or Baleen plates. Each of these is triangular, with a 

 thick, smooth outer edge, somewhat concave from above 

 downwards, which, in the natural position of the plates, is 

 nearly vertical, and is covered by the great lower lip. The 

 upper edge of the plate, also slightly concave, is attached 

 to a transverse elevation of the gum covering the palate. 

 Vascular papillae extend from this ridge into cavities of cor- 

 responding dimensions, which lie, parallel with one another, 

 in the baleen plate. The third side of the triangular baleen- 

 plate, somewhat convex and sloping from the middle line 

 above, downwards and outwards, gives origin to a number 

 of filamentous processes, into which the baleen appears to 

 be, as it were, frayed out. When the mouth is shut, these 

 frayed edges of the numerous and close set baleen plates, 

 which are longest in the middle of each series, and shortest 

 at each end, enclose a cavity, the bottom of which is occu- 

 pied by the large and fleshy tongue. By raising the 

 tongue, whatever solid matters are inclosed in the mouth 

 can be forced back into the pharynx and swallowed ; while 

 the water in which they were suspended is driven out 

 between the baleen-plates. The Whale feeds by putting 

 this gigantic strainer into operation, as it swims through 

 the shoals of minute molluscs, crustaceans and fishes, which 

 are constantly found at the surface of the sea. Opening 

 its capacious mouth, and allowing the sea water, with its 

 multitudinous tenants, to fill the oral cavity, the Whale 

 shuts the lower jaw upon the baleen plates, and straining 

 out the water through them, swallows the prey stranded 

 upon its vast tongue. 



In some of the Balcenoidea, e. g., Balwna rostrata, the 



