No. 433.] CERTAIN GROUPS OF BIRDS. 



63 



in Sula. Compressed transversely, it was distinctly triangular 

 upon lateral aspect. 



Marsh observed that the fibula of H. regalis agreed essen- 

 tially with that of Podiceps, and, as in that genus, the entire 

 skeleton of the limb is non-pneumatic. " In the adult Hes- 

 perornis, the second, third, and fourth metatarsals are thor- 

 oughly coossified into a stout, transversely compressed bone of 

 moderate length, but in most specimens traces of the sutures 

 remain. The fourth metatarsal element so greatly exceeds the 

 other two in size, that it forms by far the greatest part of the 

 entire tarsometatarsal bone. 



" The first metatarsal is not coossified with the main shaft 

 of the tarsometatarsal bone, but is a mere remnant, united to 

 the lower half of the second by cartilage [ligament?]." 



Different species of Hesperornis, as H. crassipes, H. gracilis, 

 and H. regalis, exhibited marked characteristic differences in 

 the various bones of their skeletons. But they were only of 

 specific value. 



Of the skeleton of the foot in H. regalis, Marsh wrote that 

 the feet of " Hesperornis resembled more closely those of the 

 genus Podiceps than of any other birds. The number of 

 digits is the same, the number of phalanges in each digit iden- 

 tical, but the proportions of the latter are different and quite 

 peculiar. In Podiceps, and the other grebes, the outer toe is 

 the longest, but the middle one almost equals it in length and 

 size, while the second is but slightly smaller. In Hesperornis, 

 however, the fourth or outer toe is the dominant one, being 

 three or four times as powerful as the adjoining one, or as the 

 other three combined. Again, the phalanges in Podiceps are 

 very elongated and slender, and the terminal ones spatulate, 

 while, in Hesperornis, the phalanges are short and thick, with 

 the terminal ones more or less pointed. The phalanges in 

 Hesperornis are, in fact, shorter than in most swimming birds, 

 and in their individual proportions remind one of the toe bones 

 of the penguins" (Odontornithcs, pp. 99 and I0 °)- 



Fossil remains of many other birds have been discovered in 

 the cretaceous formation in different parts of America, and a 

 number of these have been described and named by Marsh 



