230 OSTEOLOGY OP ANSERES. 



of equal Iengtb. They Conn tlie grooves for the usual tlexor tendons 

 passing to the toes. 



Notwithstanding their lateral compression, the trochlear of the distal 

 end arc very large, their median grooves distinct, and carried all the 

 way around. The inner trochlea is elevated upon the shaft, and only 

 descends as far as the base of the middle one. It is also turned slightly 

 inward, and at the same time projects the farthest behind. The usual 

 foramina] perforation is seen in the furrow between the middle and 

 oilier trochlea', just above the cleft that divides them. 



We find the accessory metatarsal of a moderate size and elevated far 

 above the inner trochlear projection — not articulating with the shaft of 

 the tarso-metatarsus, as in many birds, but attached to a ligamentous 

 structure stretching between the lower part of the hypotarsus and the 

 trochlea above mentioned. 



The hind toe which it supports is fully developed, with basal joint 

 and claw, though it is proportionately much smaller in comparison with 

 the three anterior toes witli their large joints. 



These latter need no special description, they are articulated and fash- 

 ioned as in the anserine fowl generally, as well as being conformable 

 with the most usual arrangement in regard to number of joints allotted 

 to the several toes. We may fancy that a certain amount of lateral 

 compression is present in the phalauges of these podal digits, but if it 

 is so, it is very slight, being little more in degree than is enjoyed by 

 like skeletal parts in the feet of the .1 natincc. To present the characters 

 of the skeleton of the Anatinas more in detail, I have chosen for the 

 purpose a specimen of the common Spoon-bill Duck {Spatula clypeata) 

 and will now rapidly review its osteology. 



OSTEOLOGY OF SPATULA CLYPEATA. 



So far as its skeleton goes this bird is very closely allied to the Teals, 

 a fact that perhaps might not be suspected on first sight from external 

 appearances alone. Beyond its increase in size, the chief point in de- 

 parture from this genus is seen in the enormous development of the 

 premaxilla and a corresponding enlargement of the mandibles (Figs. 1-1 

 to IS, I'm.r.). 



In the dried and properly prepared skull of Spain hi, this premaxilla 

 is an elegant, symmetrically formed, yet delicate scroll of bone, and, so 

 tar as I am aware, unequaled by any similar structure among verte- 

 brates. At the middle part of the anterior arc there occurs a thicken- 

 ing, winch in life supports the "nail" of the integumental sheath. 

 Both this and the region on either side is quite thickly studded with 

 foramina. 



The external narial apertures are placed well back, as may be 

 seen in Figs. 15 air! 10, they being of a snbelliptical outline. Com- 

 paratively speaking, these openings are considerably larger in the 

 Swans and Geese, while in such a form as (Uaucionetta islandica they 



