BRITISH FOSSIL CRETACEOUS BIRDS. 505 



The Femur. (PI. XXVII. figs. 1-12.) 



More specimens of femur have been found than of any other bone. 

 The Woodwardian Museum contains twenty-four, of which eight are 

 proximal ends. This is nearly half the total number of specimens 

 of bird-bones in the Museum. In the collection of Mr. T. Jesson, 

 F.G.S., in which there are seventeen bird-bones, six are fragments 

 of femora — five of them distal ends, and one proximal. On the 

 lowest computation these remains alone must have pertained to at 

 least thirteen birds. The femora differ in size, form, and slender- 

 ness, but not to a marked degree ; so that if the bones belonged 

 to three different species, as is probable, they all may have been 

 closely allied. The smallest femur is rather longer than that of the 

 Red-throated Diver, but has the articular ends less expanded. One 

 specimen in Mr. Jesson's collection (figs. 1, 2, 3) is ]| inch long, 

 but has both articular ends worn and short of their true length. 

 It is bowed superiorly, much as in the Diver, being concave in length 

 interiorly and convex superiorly. The shaft measures ^ inch from 

 within outward in the middle, and widens proximally to -J inch as 

 preserved, and distally to T ^ T inch as preserved. 



The external surface is flattened, somewhat pitted with muscular 

 attachments, rounded into the anterior and posterior surfaces, and is 

 concave from the proximal to the distal end. The antero-posterior 

 diameter of the shaft in the middle is more than \ inch, but becomes 

 somewhat less towards both ends. The internal surface is somewhat 

 compressed on the posterior margin, but is well rounded in the shaft 

 from back to front, though towards the extremities it becomes more 

 compressed. The proximal end is subtriangular when seen from 

 above, the superior antero-posterior external measurement being 

 much more than in Colymbus, while the articular head of the bone 

 is smaller ; and the shaft is slightly compressed superiorly external 

 to the articular head, the impression being greatest in front. The 

 distal end is marked in front with a shallow broad channel, nearly 

 the width of the anterior surface, margined on the inner side by a 

 sharp ridge, which is the edge of a flattened, narrow, short inner 

 surface that, looks inward and backward. As usual in birds, the 

 proximal and distal articulations are both in the same plane, and 

 the outer distal articular surface is the larger of the two. 



Another femur, imperfect proximally (fig. 8) (presented to the 

 AYoodwardian Museum by Rev. T. G. Bonney, F.G.S.), appears to 

 have been shorter and stouter, approaching nearer to that of the Diver, 

 and the muscular attachments very like those of the Diver. As 

 preserved, the fragment is lj inch long and -f^ inch wide in the 

 middle of the shaft ; distally it is about | inch wide. At the 

 distal end there is wide pit rather than a groove, resembling that in 

 the Red-throated Diver, only not so deep. 



A third femur, badly preserved distally, and showing no trace 

 proximally of the articular end, is If inch long ; distally it is f inch 

 wide, while the larger condjde measures -| inch from front to back. 

 This indicates an animal somewhat larger ; but it is difficult, with 



