96 ODOXTORXITHES. 



deep groove between the third and fourth metatarsal elements. This 

 groove begins above in the fossa, just beneath the superior articulation, 

 and it becomes deeper throughout its lower half, and ends in the foramen 

 between the third and fourth* metatarsals, just above the distal condyles, as 

 iu the corresponding bone in Podiceps, and many other recent birds. There 

 is a shallow groove, also, between the second and third metatarsals, which 

 commences above, in the fossa already mentioned. 



The fourth metatarsal terminates below in a prominent free 'articular 

 end, somewhat resembling, in general form, the distal end of the tibia. 

 This extremity is truncated, nearly at right angles with the axis of the 

 bone, and it projects considerably below the adjoining articular end of the 

 third metatarsal. The inner condyle is much more prominent than the 

 outer, especially in front. 



The third metatarsal element is scarcely one-third the size of the 

 fourth, and is placed somewhat behind, and back of it. The distal extremity 

 is hence oblique, and the inner condyle is smaller than the outer. 



The second metatarsal element is still smaller and shorter, but its 

 distal free extremity is but little inferior in size to the third. When the 

 tarso-metatarsal bone is seen from the front, the third element is almost 

 entirely concealed. 



The first metatarsal is not coossified with the main shaft of the 

 tarso-metatarsal bone, but is a mere remnant, united to the lower half of 

 the second by cartilage. Its place of union is indicated by an elongated 

 oval indentation, on the inner margin of the second metatarsal, above its 

 articular extremity. 



In Hesperomis crassipes, the tarso-metatarsal bone presents some inter- 

 esting points of difference from that of Hesperomis regalis. It is stouter 

 and more massive, and on the inner side of the upper half there is a large 

 tuberosity, somewhat similar to the ossified support of a rudimentary spur 

 (Plate XYII). This tuberosity is of equal size on each of the two meta- 

 tarsals of the type specimen, number 1474. The sutures uniting the three 

 metatarsals are well marked in this species. The large rugosity on the 



