486 STRUCTURE AND CLASSIFICATION OF BIRDS 



PYECRAFT'S careful description 1 of Calodromas (which I can 

 confirm) and Rhynchotus rufcscens. In the former bird the 

 body is fairly covered with feathers, the apteria being narrow. 

 There is no down save on the wings. The spinal tract soon 

 divides into two ; but they rejoin near the base of the neck. 

 These tracts again divide and reunite some way in front of 

 the oil gland, enclosing thus a dorsal apterion. The ventral 

 tracts also divide early upon the neck, and each of them 

 again divides on the pectoral region into a stronger, outer, 

 and a somewhat weaker, inner, tract. Until about halfway 

 down the neck the dorsal and ventral tracts are in contact. 

 In Rhyndiotiis rufescens there is no spinal apterion. The 

 after shaft is much more rudimentary than in Calodromas, 

 where it is well developed. Both birds have ten feebly 

 developed rectrices. Rh. perdicarius has eight. 



The aftershaft is apparently in the process of disappear- 

 ance among the tinamous. In Nothocercus, writes Mr. PYE- 

 CRAFT, ' it is evidently degenerating, inasmuch as the shaft 

 is almost, if not quite, obsolete, only the rami remaining.' 

 In Tinamus solitarius the aftershaft is absent. Powder- 

 down pat dies exist in a few tinamous. They occur, for ex- 

 ample, in Tinamus major. In Cryptu rus ta ta upa the powder- 

 down patches extend down 011 each side of dorsal tract from 

 a little in front of humerus nearly to oil gland. After the 

 end of the scapula they thicken and spread outwards as far 

 as the head of the femur, and are in contact for nearly two 

 inches along mid-line ; they then narrow again and terminate 

 half an inch in front, and slightly to the side, of the oil 

 gland. 



Rhynchotus perdicarius has apparently no powder- 

 downs. 



The tongue of the tinamous is small and triangular in 

 form. The crop is present and large. The provcntricitlus 

 is zonary ; the liver subequilobed, with a gall bladder. 



The following are measurements of the alimentary 

 canal : 



1 Ibis, 1895, p. 1. 



