5-54 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



Fig. 6.— Right coracoid and portion of 

 LEFT SCAPULA OF Baptomis adveuus, 



NATURAL SIZE. 



The extraordinary thing about them is that short as thc}^ are they ar(> 

 perfectly formed and possess the muscular insertions of much larger 

 bones, while it is evident that the bones of the manus were also pres- 

 ent. This is quite different from Hesperornis, in 

 which the humerus is rather long and straight, and 

 the bones of the forearm and manus absent; it carries 

 to an extreme conditions found in the great auk, a 

 bird in which the forearm is much reduced, though 

 still functional, Baptornis thus pre- 

 sents the peculiarity of a forearm of 

 diminutive size, whose bones are per- 

 fectly formed, bear the muscular im 

 pressions of much larger wing l)ones, 

 and imply the presence 

 of quill feathers, and not 

 improbably the use of the 

 wings in conjunction with 

 the feet in aquatic loco- 

 motion. In other birds 

 in which the wings have 

 undergone extensive reduction, such as Rhea and Struthio, 

 to say nothing of Apteryx, the radius and ulna lack the 

 well-defined form and muscular ridges of Baptornis. 



The femur, while short and stout, has nothing of the 

 squareness shown by Hesperornis, but reseml)les rather 

 that of a loon on a more massive scale. The greater 

 trochanter is slightly raised above the level of the head 

 of the femur, and the outer condyle extends below the 

 level of the inner; the antitrochanter also appears to have 

 locked slightly downward, so that the position of the leg 

 in swimming was doubtless like that of existing water- 

 fowl. This is the ordinary arrangement and would not 

 be specially mentioned but for the fact that it is the 

 reverse of these conditions, coupled with the character of 

 the tibio-tarsal joint that causes the tarsus of Hesperornis 

 to stand out almost at right angles to the bod3\ The 

 procnomial process of the tibia is higher than in Hesper- 

 ornis, and the large patella appears to have articulated 

 on one side of this, somewhat as in grebes, and not as in 

 jH'nguinsand cormorants, where the patella functions as 

 a cnemial process. The patella is large, of a modified tri- 

 hedral form, and has a large perforation for the ambiens. 

 The taxonomic value of such a perforation is lessened ])y the fact that 

 among cormorants such a perforation is present in some species and 

 absent in others, and while this may prove to be correlated with 

 other characters the available material does not show this. 



Fig. 7.— Left hu- 

 maeus, radius 

 and ulna of 

 liaptornin ad- 



VOfVfS, NATURAL 

 SIZE. 



