452 STRUCTURE AND CLASSIFICATION OF BIRDS 



The skin in these birds is excessively emphysematous, 

 save only on the shoulder, and in Palamedea and Chauna 

 derbiana on the tibia. The feathers, however, do not per- 

 forate the cutaneous air cells, ' but cause the skin to be 

 indented where they are inserted.' The aftershaft, though 

 present, is confined to the feathers on the nape of the neck. 

 The rectrices are twelve in Chauna and fourteen in Palame- 

 dea. The oil gland in Ch. derbiana has a single orifice on 

 each side ; it is encircled by feathers which constitute the 

 tuft. 



In Gh. char aria the summit of the oil gland is covered 

 by feathers, a line of which separates the two orifices of the 

 gland. In Palamedea the same is the case, but the encircling- 

 ring of feathers is not complete on the ventral side. The 

 pterylosis is almost unique in the fact that there are no 

 apteria, except, indeed, a space in the axillary cavities, and 

 these are covered with down feathers. The strong horny 

 spur borne on a bony core, an outgrowth of the first meta- 

 carpal, is comparable to a thickened featherless patch of skin 

 in a corresponding situation in Sarcidiornis. 1 



The patagialis muscle is not reinforced by a biceps slip ; 

 the brevis tendon is single, but broad, and without a patagial 

 fan. The expansor secundariorum is present and ' ciconiine.' 

 The insertion of the deltoides posterior is extensive in Pala- 

 medea for about three inches down the humerus. The 

 anconaus has a well-marked humeral head. The division of 

 the biceps commences in the fleshy belly of the muscle. 

 In all the members of this family a very peculiar muscle 

 exists, to which Mr. MITCHELL and I have given the name of 

 costo-sternalis externus. It arises from the third, fourth, 

 and fifth ribs by a tendinous head, and is inserted on to the 

 costal edge of the sternum half an inch from the posterior 

 end. 



The muscles of the leg are complete, as regards those 

 upon which GAEROD laid stress in his classification, in 

 Chauna. In Palamedea, however, the accessory femorocau- 

 dal is absent. The biceps has not an anserine insertion, but 



1 Not, of course, to the carpal spur of Plectropterus. 



