IIALLI 325 



by two yellow elastic pads of tissue springing from the 

 membrana tympaniformis. 



The genera Heliornis and Podica the former American, 

 the latter Old- World in distribution seem to require a sepa- 

 rate family for their reception. The structure of these two 

 birds has been mainly investigated by myself ; l the skeleton, 

 however, has been described by BRANDT also. 2 



In neither bird is there an aftershaft, though the oil 

 gland is tufted. Unlike other rails they are quintocubital. 

 The ptenjlosix is essentially ralline. In Hcliornis the neck 

 is nearly continuously feathered, there being only a short 

 vental apterion. The dorsal tract is strong between the 

 shoulder blades, and is forked ; the hinder parts of the tracts 

 scarcely join the anterior ; they become fused some way 

 in front of the oil gland. In Podica senegalensis, but not in 

 Hcliornis, the ventral tracts are undivided. The less degree 

 of specialisation is seen in other features of the anatomy of 

 the smaller American finfoot. 



The muscle formula of the leg in both genera is ABX + , 

 the Y of the rails not being developed. The chief peculiarity 

 of the leg muscles, however, concerns the biceps. This is a 

 very large muscle ; in Podica it has no less than three 

 separate insertions on the leg. First there is the ordinary 

 insertion through a perfectly normal sling ; just before this 

 tendon a branch is given off which is inserted independently 

 on to the leg some way further down. In addition there is 

 an extensive insertion on to the fascia covering the calf of 

 the leg. In Heliornis the muscle is somewhat simplified, 

 only the first and third insertions being present. The 

 complications of the biceps may have some relation to 

 swimming; for in certain auks (q.v.) there is a similar 

 gastrocnenial attachment. 



1 ' On the Anatomy of Podica senegalensis,' P. Z. S. 1890, p. 425 ; ' On the 

 Osteology, Pterylosis, and Muscular Anatomy of the American Finfoot (Heliornis 

 surinamensis),' Ibis, 1893, p. 30. 



2 ' Beitrage zur Kenntniss der Naturgeschichte der Vogel,' etc., Hem. Ac. 

 Sci. St. Petersburg, 1840, p. 81. See also GIEBEL, ' Zur Naturgeschichte des 

 surinamischen Wasserhuhns Podoa surinam-ensis,' Zeitsclir. yes. Natunr. xviii. 

 1861, p. 424, and NITZSCH'S Ptcrylograplnj. 



