CRIBKATORES. SIFTERS. 575 



In the Swans the skeleton is also strong. The skull is 

 more elongated, the interorbital space broader, the maxillary 

 bones longer and less strong, both more concave. The neck 

 is extremely long, with twenty-two vertebrae ; the dorsal 

 ten, the lumbar and sacral fifteen, the coccygeal seven. The 

 pelvis is longer and narrower. There are ten flattened ribs, 

 the first and four last without processes, and the last not 

 connected with either the spine or the sternum. The latter 

 is narrower than in the Geese, but otherwise similar, only 

 the carina is generally hollowed for the reception of a curve 

 of the trachea ; in which case there is a hollow on the fork 

 of the furcula, which is more slender, narrower at the fork, 

 and more curved than in the Geese. Unless as to length, 

 the wings and feet are as in them. 



The Ducks have the skeleton proportionally less stout, 

 with the head more like that of the Swans than of the 

 Geese, the skull less elevated, and the jaws more flattened. 

 There are from fourteen to sixteen cervical vertebras, eight 

 dorsal, fourteen lumbar and sacral, seven coccygeal. Of the 

 nine slender ribs the first and two last have no processes, 

 and the last has an appendage projecting backwards from 

 the upper end of its sternal portion. The pelvis is long, as 

 in the Swans. The sternum of moderate length, broadish, 

 with two deep notches behind. The furcula is moderately 

 stout and arched. The cubital bones a little shorter than 

 the humerus. 



The Diving Ducks have the body shorter, as is the neck, 

 in which, however, the vertebras are from fourteen to sixteen. 

 The jaws are shorter and broader. The dorsal vertebrae 

 eight, the lumbar and sacral twelve, the coccygeal seven. 

 The pelvis is shorter and broader, as is the sternum. The 

 furcula less curved. Of the ten ribs the first and two last 

 have no processes. The tarsal bone is shorter and narrower 

 than in the Ducks ; but the bones of the wing are similar. 



One skeleton graduates into another, as is the case with 

 the exterior generally, and the organs in particular. With- 

 out attempting to define the groups by unvarying characters, 

 let us see in what respects they agree. 



The body in all is large, full, and muscular, with a thick 



