The Gruiformes, which lie between the Galliformes and the Charadriiformes, compose a somewhat heterogeneous Order, which includes forms so different as the _Rallidae_ (Rails), _Gruidae_ (Cranes), _Aramidae_ (Limpkins), _Psophiidae_ (Trumpeters), _Cariamidae_ (Seriemá and Chuñia), _Otididae_ (Bustards), _Rhinochetidae_ (Kagu), _Eurypygidae_ (Sun-Bitterns), and _Heliornithidae_ (Finfoots). Of these a large number are Waders, but the Land-Rail, the Wekas, the Kagu, the Bustards, and others, cannot be classed in this category. All agree in having no true crop, a tracheo-bronchial syrinx, and an elevated hallux; while the front toes are never completely webbed, though nearly so in _Heliornis_; the nares, moreover, are pervious, except in _Rhinochetus_. In the last-named the condition of the newly-hatched young is unknown, in _Heliornis_ they are said to be naked at first, but in the remainder of the group they are covered with simple down. In structure the nine Families differ widely, a fact which would seem a strong argument against combining them under one head; but the aggregate of such points must be considered, and in any linear system the relationships within every Order cannot possibly be equally close. The present arrangement does not differ greatly from that adopted by Mr. Sclater,[171] wherein he accepted the names _Alectorides_ and _Fulicariae_, used by Nitzsch, but made the former to consist of the _Aramidae_, _Eurypygidae_, _Gruidae_, _Psophiidae_, _Cariamidae_, and _Otididae_, and the latter of the _Rallidae_ and _Heliornithidae_. Some writers, both modern and ancient, have placed the _Otididae_ in the Limicoline group.