326 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



resembles a wedge, the anterior or sharp margin of which is directed 

 forwards, the base backwards towards the femur. The base of the 



wedge is broad, deeply concave, and 

 adapted to the pulley-like surface of 

 the lower end of the femur. The outer 

 surface of the bone is for the most part 

 smooth, but presents about its middle 

 a deep and narrow groove, which, com- 

 mencing in front at the middle of the 

 anterior border of tlie bone, passes ob- 

 liquely backwards, downwards, and 

 outwards across the external surface. 

 This groove accommodates the tendon 

 of the " ambiens " muscle. The inner 

 surface of the bone is smooth. The 

 upper end of the patella is obliquely 

 truncated, and aflbrds insertion to the 

 muscular libers of the extensor cruris 

 muscle, while the lower end, narrower 

 and more irregular in form, is attached 

 by means of very short ligamentous 

 fibers to the anterior border of the 

 upper end of the tibia. The patella 

 presents essentially the same charac- 

 ters in every species." This descrip- 

 tion answers very well for AptenodyteSj 



Fig. 1. -Leg-bones and patella, right limb, of OUly thiS latter PeUguln haS the pa- 

 ^p<enodj/«e,sp«rtnnnfu'; life-size from nature. , ,, , , -n , 



T, tibia; F, fibula; p, patella; the last tclla much larger, as Will be seen in 



slightly raised above its articulation with ^ , /, r i l • ■ . n 



tibia. (No. 11976, Smithsonian Collection.) thC ngUrC. Ill ThC great majority Of 



By the author. A, \}a.te\\a. of Eudy pies chry- -, ■ ^ , ,,, •.-,•/■ ■• 



socome (from Triston d'Acuha) outer sur- bll'ds WhcrC a patella CXIStS it IS fOUUd 



face, natural size. B, the same seen from ii ^\ i- v iij.i 



in front (after Watson). to havc the lorm ot au oblatc hcmis- 



pheroid, with its base directed up- 

 wards for insertion of the extensor cruris. A very good example of this 

 is seen in our common eastern crow (Fig. 2), and it is this bird I have 

 chosen to illustrate this style of patella in the figure (C). We find it 

 associated in the cut with two other rather extraordinary i)atellfe, that of 

 Mergus serrator (D), and Sula hassana (E). The bone in the double patella 

 of Mergus is of a very elementary character, indeed almost cartilaginous 

 in appearance and consistence. This bird, we see, approaches very near 

 not having any patella at all. The best example I have of this condi- 

 tion is seen in two specimens of Hccmatopus niger from the collections 

 at the Smithsonian Institution. Here, in these birds, I fail to find the 

 slightest trace of this sesamoid. 



Professor Marsh tells us that the patella of Sida is perforated by a 

 large foramen for the passage of the tendon of the ambiens muscle, 

 agreeing in this respect with the fossil bird Hesperornis (Ordontorni- 



