No. 433. J CERTAIN GROUPS OF BIRDS. 



foramen of the femur in the ostrich is situated posteriorly 

 rather than in front, as it is in nearly all other birds, while the 

 "epicnemial process" of the tibiotarsus "extends forward, 

 without rising above the level of the proximal surface, and con- 

 tracting to its termination, there divides into small pro- and 

 ecto-cnemial processes ; the latter the shortest and tuberous." 



As for pneumaticity, the bones of an ostrich enjoy a greater 

 degree of it than do those in the case of any of the true 



Struthio camelus is, with respect to existing birds, most 

 nearly related to the South American ostriches, the various 

 species of Rhea. 



The late T. J. Parker, in his admirable memoir "On the 

 Cranial Osteology, Classification, and Phylogeny of the Dinorni- 

 thidae " {Trans. Zobl. Soc, London, Vol. XIII, Part XI, October, 

 l8 95)> gives very complete tabular schemes comparing the 

 cranial characters of several of the supersuborders of the Dro- 

 maeognathae, and from these it will be seen that a number of 

 excellent characters distinguish the cranium of Struthio from 

 that of Rhea. 



Suborder II. Rheornithes. 



Family: Rheuxe. 



In the genus Rhea, the only genus of the present family, are 

 contained those ostrich-like birds of South America, commonly 

 known in Europe as nandu. According to Newton there are 

 at least three species of these, vis., R. americana, R. darwini, 

 and R. macrorhycha. Considerable has been written upon their 

 osteology, but more particularly has the skeleton of Rhea ameri- 

 cana been described, which received the attention of Huxley, 

 of the Parkers, and of not a few others. Nearly all recent 

 authoritative taxonomers place these birds in an order, coequal 

 with the order occupied by the ostriches proper (Struthio). 



Some of the special osteological characters of Rhea have 

 been pointed out by Huxley, thus : 



1. The maxillary processes of the palatines are short and 

 unite with the inner and posterior edges of the maxillo- 

 palatines. 



