FEET OF HESPERORNIS. 105 



This articulation shows an approach to the crescent and peg structure, but 

 in its main features resembles the usual phalangeal joint in birds. 



The second phalanx in this digit (Plate XVIII, figure 6), is much 

 shorter than the first, somewhat less compressed, but" in other respects, 

 very similar. The shaft is nearly straight, and but very slightly excavated 

 on its outer inferior surface. 



The third phalanx (Plate XVIII, figure 7) is materially longer than 

 the second, and much more slender. It shows the same tendency toward 

 horizontal flattening, seen in the penultimate phalanx of the outer 

 toe, the advantage of which has been explained above. The proximal 

 articulation is subcircular in outline, and moderately concave. The distal 

 extremity is much compressed. 



The fourth, or terminal, phalanx of this digit has not been recovered, 

 but the articulation which supported it, and the shape of the ultimate 

 phalanx of the second toe, indicate its form and general proportions, which 

 are represented in Plate XX. 



The principal dimensions of the phalanges in the third digit of 

 Hcsperornis regalis and Hesperomis crassipes are as follows : 



^Measurements of First Phalanx of Third Digit. (Hesperomis regalis, Xo. 1200.) 



Length of first phalanx, 41.0 mn 



Greatest vertical diameters of proximal end, 18.-19.0 



Least vertical diameter of proximal end, 14.0 



Transverse diameter of proximal end, 10.0 



Greatest vertical diameter of proximal articulation, 14.0 



Least vertical diameter of proximal articulation, 12.0 



Transverse diameter of proximal articulation, 8.5 



Least vertical diameter of shaft, 8.0 



Least transverse diameter of shaft, 6.2 



Greatest diameter of shaft, at distal end, 10.0 



Least diameter of shaft, at distal end, 8.0 



Greatest vertical diameters of distal articulation, 8.-10.0 



Least vertical diameter of distal articulation, 7.5 



Transverse vertical diameter of distal articulation, 7.5 



14 



