356 STRUCTURE AND CLASSIFICATION OF BIRDS 



Subfamily II. Stercorariinse. 



Muscular formula, AXY + . Gceca long. Biceps 

 slip present. Expansor secundariorum absent. 



Subfamily III. Sterninse. 



Muscular formula, ABXY+. Gceca rudimentary. 

 Biceps slip present. Expansor secundariorum 

 absent. 



Subfamily IV. Rhynchopinse. 



Muscular formula, A BXY—. Gceca rudimentary. 

 Biceps slip and expansor secundariorum absent. 



Gygis and Anous require further investigation before they 

 can be placed in this system ; they are usually regarded as 

 terns — by Howabd Saunders, for example. Anous has th'e 

 complete muscle formula. Gygis has the formula of the 

 gulls; but then the tern, Sternula (sp.), wants the accessory 

 femoro-caudal, and in this approaches the gulls. Anous has 

 the expansor secundariorum. 



Of undoubted or reputed extinct limicolous birds a number 

 have been described. If PalcBotringa (with three species), from 

 North America, is rightly referred by Mabsh to this group, it goes 

 back to Cretaceous times. Milnea, from French Miocene, is known 

 by the humerus. Elorius, known by an imperfect coracoid, a tarsor 

 metatarsus, and parts of the skull, seenis to belong here, ^gial- 

 ornis is considered by Lydekkee to have been a gull-like bird, 

 largely on account of the perforated first phalanx of the second 

 digit.' Haley ornis has been described from the extremity of a 

 humerus and the back of the skull. 



Charadriidaj 



Gildicnemidse 



Parridte . 



Ciilonididre 



Thinocoridee 



G-lareolidee 



Laridee . 



Pert. 

 Notch 



Perf. 

 Notch 



Perf. 



Notch 



o 



15 

 16 

 16 

 16 

 16 

 16,16 

 15 



' A character which we have seen (suj^ra, p. 351, footnote) to be of no 

 account in fixing affinities. 



