224 THE IVORY-BILLED WOODPECKER. 



diverging, two slender apo-hyal bones, 1 inch 1 twelfth in length, each of 

 which is continuous with an extremely elongated cerato-hyal bone, 4 inches 

 and 1 twelfth in length, f twelfth in breadth at the commencement, gradually 

 tapering to a blunt point, convex on its lower surface, concave or channelled 

 on the upper, passing under and internally of the articulation of the jaw, and 

 curving upwards along the occiput, until the two meet on the top of the 

 head at the level of the posterior margin of the orbit, in the median line of 

 the cranium, which is much depressed, whence they proceed in mutual 

 contact, inclining slightly to the right side, and terminate a little before the 

 anterior margin of the orbit, half an inch behind the right nostril, and a 

 quarter of an inch from the base of the bill. These prolongations of the 

 os hyoides being of an osseo-cartilaginous texture, are possessed of much 

 elasticity, so as in some measure to resemble a curved spring. 



From near the angle or point of union of the two crura of the lower man- 

 dible internally, there proceeds on each side a slender muscle, o o, which, 

 running backwards, comes in contact with the prolongation of the hyoid 

 bone at the joint between the apo-hyal and cerato-hyal portions, and is 

 thence continued along the whole extent of the latter, o g, o g, running 

 chiefly along its upper side, but partially enclosing it, and bound to it by a 

 sheath of cellular tissue, which allows it considerable motion. The bone and 

 muscle are together enclosed in an extremely delicate, transparent, tenacious 

 sheath, moistened internally with a serous fluid, and terminating at the end 

 of the bone, where it is attached by elastic tissue to the cellular substance 

 and periosteum near the base of the bill. This delicate sheath, perfectly 

 smooth and lubricated on its inner surface, is on the outer attached by deli- 

 cate filaments to the dense cellular tissue which forms a kind of external 

 sheath. It is fixed in its place, and the hyoid bone with its muscle, g g, 

 slides backwards and forwards in it. 



The entire length from the tip of the tongue, c, to the tip of each prolon- 

 gation of the hyoid bone at e, is 7 inches 2 twelfths. The protrusion of the 

 tongue is effected by the contraction of the slender muscle above described, 

 o, which having a fixed basis in the lower jaw near its angle, and acting upon 

 the tip of the hyoid bone, which is in this bird situated anteriorly to the 

 eye, on the forehead, near the base of the upper mandible at c, causes the 

 hyoid bone to glide within its sheath until its tip has moved backwards over 

 the forehead, the crown, and occiput, and then advanced forwards until 

 beneath the articulation of the lower jaw, thus traversing a space of 3^ 

 inches; so that the tongue is protruded to 3 inches and 4 twelfths beyond 

 the tip of the bill. When the muscle is relaxed, the parts regain their 

 ordinary position by the aid of the elasticity of the prolongations of the 



