142 



CHAEADEIUS. 



Size the 

 most easy 

 character. 



Sections of 

 the sub- 

 genus. 



There is one notable exception to this rule in C falklandicus, which is one of the larger 

 species, but has nearly black central upper tail-coverts. In some examples of C. nivosus 

 and C. coUaris the difference of colour between the central upper tail-coverts and the rest 

 of the upper parts is not very striking. 



The most obvious character by which the Sand-Plovers may be divided into two 

 groups is that of size, but here again it is difficult to find a hard-and-fast line. Three 

 species appear to be intermediate — C. wilsoni, C. sanda-helence, and C. occidentalis. They 

 vary in length of wing from 4*5 to 4-8 inch. All the other species fall naturally into two 

 groups — one containing the small species, in which the wing from the carpal joint measures 

 4-5 inch or less ; and the other containing the large species, in which the wing measures 

 4-8 inch or more. The relationship of the three species which are intermediate in size is 

 not very easy to determine, but that of the two latter is with the group of small-sized 

 species, and that of the former probably with the larger species. In order to place them 

 there the definitions of the two sections of the subgenus must stand as follows : — 



^GiALOPHiLi MAJORES. — Length of wing from carpal joint 4f inches or more. In 

 order to exclude the two species which occasionally reach this size, but obviously belong 

 to the next group, and to include the one which occasionally falls short of it, no species 

 can be admitted (1) with black legs if the lores be white, (2) nor with the primary-coverts 

 much (about \ inch) shorter than the outermost secondaries ; (3) nor under any circumstances 

 can a species be excluded if the terminal vault of the bill measure as much as '4 inch. 



iEoiALOPHiLi MiNORES. — Length of wing from carpal joint 4^ inches or less. In 

 order to include two species which occasionally slightly exceed these dimensions, and to 

 exclude one which occasionally comes within them, jEgialopliili possessing either of the 

 two following characters must also be included : (1) black legs associated Avith white lores, 

 (2) primary-coverts much (about \ inch) shorter than the secondaries; and (3) no species 

 can be admitted with a bill the terminal vault of which measures as much as '4 inch. 



The two groups thus defined appear to be natural ones, though it has been necessary 

 to resort to artificial and somewhat complicated characters to make them so. It is worthy 

 of note that with one exception, C. cantianus, all the small species breed in the Tropical 

 Region ; and with only one exception, C. wilsoni, all the large species breed in the 

 Temperate Region. 



jEGIJLOPHILI majojres. 



^GiALOPHiLi aut alis longioribus (120 ad 180 millim.) ; aut maxillse arcu longiore (10 ad 13 millim.) : 

 specie pedibus nigris cum loris albis, at specie primariarum tectricibus quam secundarise 

 valde brevioribus (circa 13 millim.) exceptis. 



I have found it absolutely impossible to construct a perfectly satisfactory key to the 

 species of this group, for the reasons hereinafter stated. 



