LIMICOL.K 347 



guishes them from all their allies. In this family the caeca 

 are mere passeriform nipples, measuring from '15 to '2 of an 

 inch in length. 



The muscular anatomy has already been to some extent 

 treated of in connection with the structure of the entire group 

 of birds of which the present genera form a family. In all 

 of them, Pa rra, Hijdropliasianus, and Metopidius, the mus- 

 cle formula is complete, i.e. ABXY+ . The condition of the 

 deep flexor tendons of the foot is very singular. As FORBES 

 justly pointed out, the peculiarly large size of the hallux (as 

 of all the digits) of the foot in these birds seems to be un- 

 reconcilable with the entire absence of a special slip from the 

 conjoined tendon of the long flexors. ' This fact,' he thinks, 

 ' seems to indicate that the Parridse may have been developed 

 from some form with a more normal-sized foot, and a small 

 hallux which had no special long flexor, the great size of 

 their feet having been developed in accordance with their 

 peculiar habits.' 



The syrinx has a pair of intrinsic muscles. 



The skull has well-formed basipterygoid processes, but 

 no occipital foramina or supra-orbital impressions. In 

 Metopidius the radius is extraordinarily enlarged (see fig. 70, 

 p. 125). In the remaining genera there is no such modifica- 

 tion of the bone, but there is a metacarpal spur, which may 

 be of the same use, i.e. for fighting. In Parra the clavicle 

 is at its articulation further from the procoracoid than in the 

 Charadriidse, and the sternum has only one pair of notches. 

 Five ribs reach it. 1 



The single genus Chionis,- of antarctic range and some- 

 what gull-like form, makes up the family Chionididse. 



There are twelve rectrices. 



The skull is peculiar in that the grooves for the supra- 

 orbital glands end in a large foramen on each side, which is 



1 The bones of Parra albin nclia are described and figured by MILNE-EDWARDS, 

 Hist. Madagascar. 



- The peculiar sheath which covers the base of the bill and the nostrils 

 (whence ' Sheathbill ') is declared by STUDEK to be developmentally different 

 from the tube of the Tubinares. 



