Zoological Club of the Linnean Societt/. 601 



ZOOLOGICAL CLUB OF THE LINNEAN SOCIETY. 



January 23, 1827. — A paper was read, entitled Observations 

 en the Trachece of Birds, with descriptions and representations of 

 several not hitherto figured; by William Yarrell, Esq., F.L.S. 

 At its conclusion Mr. Yarrell proceeded to illustrate its subject 

 by references to numerous specimens of the Skeletons, Tracheae, 

 and other organs of Birds, which he exhibited to the meeting. 

 In the course of his observations he adverted to the lengthened 

 form of the trachea2 in the Cranes, Swans, and some Geese, and 

 remarked that the true nature and use of these convolutions were 

 but little kiioAvn ; the birds in which they exist not appearing to 

 possess any peculiar powers in connexion with them, except harsh 

 and loud voices : the more complex the structure of the trachea, 

 the more disagreeable in fact was the fiound transmitted through 

 it. He then explained at some length the anatomical distinctions 

 upon which he had founded his arrangement of the species of 

 Ducks, and pointed out the leading characteristics of each of the 

 principal divisions proposed by him. The thick and strong mus- 

 cular gizzard with its small internal cavity in the herbivorous 

 species presented a striking contrast to the thinner sides and more 

 enlarged cavity of the same part in those feeding upon fish : the 

 latter gj-adually approaching in structure to the stomach of the 

 Mergansers. With these variations in the organisation of the sto- 

 mach those of the intestines and caecal appendages were shown 

 to correspond, the latter diminishing in length from nine inches 

 to two in accordance with the nature of the food. The enlarge- 

 ment at the bottom of the tube of the trachea in the males of the 

 Ducks of the first division was pointed out as entirely composed 

 of bone, while in those of the second division it was principally 

 membranous. The series of trachea employed in illustration of 

 these facts comprehended the whole of the species known to in- 

 habit Britain. From an equally extensive series of sterna the 

 depth of the keel was shown to be equal throughout all the Birds 

 of the first division in proportion to the size of the sternum j while 

 in those of the second division it diminished gradually as the 

 power of diving increased, and exhibited a considerable approxi.. 



