THE BAL^NOIDBA. 839 



and concave inferioily. The two rami of the mandible are 

 connected only by ligament at the symphysis. 



Minute teeth are developed in foetal Haloenidce, but are 

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

 bone, or Baleen plates. Each of these is triang-ular, with a 

 thick, smooth outer edge, somewhat concave from above down- 

 ward, 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 trans- 

 verse elevation of the gum covering the palate. Vascular 

 papillee extend from this ridge into cavities of corresponding 

 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, downward and 

 outward, 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 plate:^, which are longest in the middle 

 of each series, and shortest at each end, enclose a cavity, the 

 bottom of which is occupied by the large and fleshy tongue. 

 By raising the tongue, whatever solid matters are enclosed in 

 the mouth can be forced back into the pharynx and swallowed ; 

 while the water in which thej' 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 con- 

 stantly 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 JSaloenoidea, e.g., Jial(^na rostrata, the 

 cricoid cartilage and the rings of the trachea are incomplete 

 in front, and a large air-sac is developed in the cricothyroid 

 space. The JBalcenoidea possess olfactory nerves and a dis- 

 tinct, though small, olfactory apparatus. The sclerotic coat 

 of the eyeball is enormously thick, and the optic nerve is sur- 

 rounded by a rete-mirdbile. The tympanic membrane is con- 

 nected with the malleus by ligament. The semicircular canals 

 are very small, but the cochlea is large, and makes only 1^ 

 turns. The muscles of the antibrachium and manus are not 

 altogether absent. 



The right Whale [Bdlmna), and the Fin-fishes [MeffO- 

 pt^a, BaloBnoptera, etc.), belong to this division. 



