IVORY BILLED WOODPECKER. 331 



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 man- 

 dible 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 ad- 

 vanced 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 elas- 

 ticity of the prolongations of the hyoid bones, and the action of another 

 pair of muscles, to be presently described. 



The tongue, d, is covered externally with a dense sheath of fibrous 

 tissue. On its lower surface is seen on each side a very slender mus- 

 cle, commencing at the extremity of the glosso-hyal bone, and running 

 along the whole length of the basi-hyal bone, as well as of the apo-hyal, 

 to be inserted into the cerato-hyal, at the distance of one inch from its 

 base, on the outer edge. The action of this muscle, which has a strong 

 tendon in its whole length, is to bend the tip of the tongue downwards, 

 or to move the horn of the hyoid bone outwards. It may be called the 

 glosso-hyal. It has another tendon rimning parallel to that mentioned, 

 along its upper edge, of which the action must be to bend the tongue 

 upwards upon the apo-hyal. Besides these muscles, there is another 

 pair, forming the greater part of the fleshy portion of the tongue. They 

 commence at the tip of the basi-hyal bone, or at d, proceed along the 

 upper surface of the tongue, and, after running a course of 2| inches, 

 pass along the anterior surface of the thyroid bone, wind along its edge, 

 and are inserted near the middle surface of the trachea, about its tenth 

 ring. The action of these muscles, alluded to at the end of the last 

 paragraph, and marked n n, is to retract the tongue, when extended, 

 as well as to pull forward the larynx. 



Another pair of very slender muscles, mm, commence upon the edge of 

 the thyroid bone externally of those last described, separate immedi- 

 ately from the trachea, pass directly down the neck in front, under the 

 subcutaneous muscle and skin, to which they are firmly attached by 

 cellular tissue, and are inserted into the furcular bone about the middle 

 of its length. These muscles, the cleido-tracheales, are not peculiar to 

 Woodpeckers, and have nothing particular to do with the movements 

 of the tongue in those birds. 



