206 THE NATUKAL HISTOBT OP 



a swelling. The internal structure of this memuer, 

 in the Mono Colorado of Humboldt, is thus described 

 in his Zoological Observations, and will serve as a 

 model for the others. " The bony case of the os 

 hyoides, measured by water, gave a size equal to four 

 cubic inches ; the larynx was slightly attached by 

 muscular fibres, and communicated by a membranous 

 canal. The larynx consisted of six pouches of ten 

 lines in length, to from three to five in depth. These 

 pouches resemble those of the small whistling monkeys, 

 squirrels, and some birds. They have an opening 

 above on the same side with that of the glottis, by' 

 which the air cannot enter without shutting the 

 epiglottis. Above the pouches there are two others, 

 of which the lips or borders are yellowish. These are 

 the pyramidal sacks which enter into the bony case, 

 and are formed by membranous partitions. The air 

 is driven into these sacks, which are from three to 

 four inches long, and terminate in a point, but come 

 in contact with no part of the large hyoid bone opening 

 below. The fifth pouch is found in the opening of the 

 arythenoid cartilage, and is situated between the pyra- 

 midal sacks of the same form, but shorter ; and the 

 sixth pouch is formed by the bony drum itself, within 

 which the voice acquires the mournful and plaintive 

 tone which characterises these animals."* The 



Humboldt, Zool. OUarr. I. p. 9. 



