92 



NATURAL HISTORY OF BIRDS. 



them with the vomer pointed in front, have two carotids and aftershaf t ; they all pos- 

 sess the ambiens muscle, as also the semitendinosus^ and the accessory slip of the 

 latter. 



Generally, the ' waders ' may be said to be littoral in their habits, only few of them 

 being exclusively terrestrial, avoiding the water as carefully as most of them do the 

 open ocean ; the shores of the sea and the lakes, the banks of the rivers, and the 

 swamps and marshes are inhabited by some form of this polymorphic group, the mem- 

 bers of which are distributed all over the globe, from the icy neighborhood of the 

 poles to the hottest regions under the equatorial sun. 



One of the most interesting of all the many interesting and puzzling forms of this 

 order are the birds which compose the super-family CHIONOIDE^. The early 

 systematists realized the isolated position of the sheath-bills, and gave the group 

 set aside for them various names, as Vaginati, Coleoramphi, etc., the curiously con- 

 structed bill being the most obvious character. But in regard to the relative taxo- 

 nomic rank of the group, opinions have differed widely, as it has been referred to 

 every possible grade from a mere genus to an order. Equally variable have been the 

 opinions of ornithologists as to their relationship, since some have referred them to 

 the Gallinaceous birds, others to the Longipennes near the gulls, others again to the 

 GrallaB. The former based their conclusions chiefly upon the most external characters 

 and the alleged gallinaceous habits of the birds, the latter took chiefly the internal 

 anatomy into consideration. And, indeed, it seems as if both those advocating their 

 place near the gulls, and those urging their affinity to the plovers and oyster-catchers, 

 are right, for the sheath-bills are so intermediate between them that it is difficult to 

 say where they should rather go, though the present writer is inclined to place them 

 with the latter. In fact they are hardly well placed before both Laroideae and Chara- 

 drioideae are united with the Chionoideas in the same order. 



Notwithstanding the external difference between the members 

 of the two families composing this super-family, their mutual rela- 

 tionship has been understood for a considerable length of time, 

 chiefly, we think, on the authority of Bonaparte, who as early as 

 1832 united them in one family. Of characters which both 

 Chionidse and ThinocoridaB have in common, it may be mentioned 

 that they are schizorhinal, that they lack occipital foramina and 

 basipterygoid processes, but have supra-orbital impressions, that the 

 ambiens muscle, as well as the femoro-caudal, with the acces- 

 sory, and the semitendinosus, with its accessory slip are present 

 (ABXY-f ), that they have two carotids, etc. The most remark- 

 able internal feature is, perhaps, the shape of the vomer, which 

 is broad and rounded in front, while in other allied forms, Ceco- 

 morphous and Charadriomorphous, that bone is pointed or bifid 

 anteriorly. The palate, indeed, in this and some other respects, 

 shows some resemblance to that of the Passerine birds, this being 

 especially the case with the Thinocorine palate, in which the vomer 

 is connected with the nasal cartilages in a manner recalling that 

 of the ^Egithognathae. 



Like many, not to say most, of those perplexing forms which represent the earlier 

 offshoots, or remain as the last survivors of groups once numerous but long since 

 decimated, the CHIONIDSE, only two species, inhabit islands in the vast oceans of the 



FIG. 39. Lower sur- 

 face of skull of At- 

 tayis grayi. 



