PASSERES 3 



XVI. Limicolae (Thickheads, Coursers, Plovers, Sandpipers, 



Snipe, Ja9anas). 



XVII. Gavise (Skuas, Gulls, Terns). 

 XVIII. Tubinares (Albatrosses, Shearwaters, Petrels). 

 XIX. Pygopodes (Divers, Grebes). 

 XX. Impennes (Penguins). 



Subclass RATIT.E (Sternum without a keel). 

 XXI. Struthiones (Ostriches). 



Order I. PASSERES. 



About six thousand, or one half the existing species of birds, are 

 included in the Passeres or " Perching Birds." 



A Passerine Bird is distinguished by a combination of several 

 characters, no one of which will alone define it. 



I. Each foot has four toes (except in Cholornis, in which the 

 outer toe is reduced to a stump), the 1st, or hind toe, directed 

 backwards ; the 2nd, 3rd and 4th forwards. The 2nd toe is 

 always the innermost. All four toes are on a level, the hind toe 

 not raised above the others, and are never connected by web or 

 membrane beyond the first joint. Owing to a peculiar arrange- 

 ment of the plantar tendons connecting the muscles of the leg with 

 the toes, the hind toe is capable of being moved independently 

 of the front toes. The tendon of the flexor longus hallucis, which is 

 inserted into the hind-toe, crosses the tendon of the flexor p erf or ans 

 digitorum, which splits up to supply the front toes, at the back of 

 the tar so -metatarsus, but without becoming connected with it, so that 

 the contraction of either muscle controls the movement of the hind 

 or front toes only, as the case may be. This " schizopelmous " 

 arrangement of the plantar tendons is found in all Passerine Birds, 

 excluding the family of Oriental Broadbills (Eurylamida) ; but it 

 also obtains in the Hoopoes (Upupida), among the Picarice (see 

 figure, p. 4). 



II. The palate is cegitliognatous, i.e., the maxillo -palatine bones 

 are separated from one another and from the vomer by an interval ; 

 the vomer is truncated in front and cleft behind so as to embrace 

 the rostrum of the basisphenoid (see figure, p. 5). This arrangement 

 of the palate-bones is however not exclusively passerine ; it exists 

 also in the Cypselidcz (Swifts) and Picida (Woodpeckers) among 

 the Picarise. 



