464 THE STRUTHIONIDAE. 
cete, and the kind of food, as well as the general mode of feeding ; 
but on the other hand the powers of flight, the feet with the hind toe 
on the same level as the others, and above all the monogamous 
character, and the helpless condition of the few young ones, so strongly 
mark them as belonging to the Insessorial order that the just conclu- 
sion is that they represent the specially Rasorial tendency among the 
hard-billed or Conirostral Insessores. There remain among the 
Rasores the families of Tetraonidae, the Grouse ; Cracidae the Cura- 
sows ; Phasianidae the pheasants and Poultry ; Struthionidae accord- 
ing to the opinion I have maintained, and Megapodidae a singular 
and little-known Australian family, without mentioning the Sheath- 
bills, which I regard as, probably, (at least if they are at all Rasorial 
birds) a special form of Tetraonidae, or the Tinamous a very interest- 
ing South American group which seem to me to be a semi-arboreal 
form of Struthionidae, and which I therefore reject from among the 
leading families of the order. It is probable that Tetraonidae stand 
first among the Rasorial birds, as the most complete development of 
the type; Cracidae, with their arboreal habits, may be placed next ; 
Phasianidae naturally follow, as the peculiarly typical or specially 
Rasorial group; Struthionidae I consider as occupying the position 
analogous with that of the order Grallatores in the larger circle; and 
I have no hesitation in regarding Megapodidae as the lowest family in 
the order. In the accompanying tabular view I give the sub-families in 
the three best known and most numerous groups, leaving the others 
for the present, as either being such small families, or our knowledge 
of them so imperfect, that nothing satisfactory could be accomplished 
in respect to them. 
The family Struthionidae is distinguished by a more or less com- 
plete mixture of the long legs and neck of the Grallatores, with the 
usual Rasorial characters, the birds being generally above the 
medium size and deficient in power of flight, which in some cases 
is entirely wanting. We could not precisely define Struthionidae 
by any one or two characters, (those generally given, as the ex- 
tremely short wings and rounded sternum, being peculiar to the 
typical sub-family SrruTHiontNas), but birds coming near the 
boundary, between Rasores and Grallatores, in which notwith- 
standing usual marks of -the latter division, the characteristics of the 
former seem, on the whole, to predominate, may be safely referred to 
this family. Dr. Geo. Gray, making the single family a distinct order 
