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BULLETIN 15 5, UNITED STATES NATIONAL MUSEUM 



where a rather broad apterium began. The spinal tract (pteryla 

 spinalis) was somewhat narrowed between the shoulders, and then 

 at the center of the scapulae, broadened gradually to form an 

 enlarged tract. This contracted suddenly behind with abrupt lat- 

 eral angles and a shallow posterior indentation on either side and con- 

 tinued in a double row of papillae to expand slightly once more 

 behind the level of the femoral attachment on the pelvis, and finally 

 terminated at the base of the large oil gland. The oil gland 

 had a prominent naked nipple and was bare except for two or three 

 scattered down feathers. There was no trace of a median apterium 

 in the large dorsal rhombus of the spinal tract. 



There were twelve rectrices. The upper coverts of all save the 

 center pair were normal and lay above the bases of the quills at their 



Figure 2. — Upper wing 

 muscles of the flat- 

 billed v i r e o law- 

 rencia nana. x 2 



Figure 1. — Dorsal ptery- 

 losis of the flat- 

 billed vireo lawrencia 

 nana. natural size. 



outer margins. The median coverts were represented only by slender 

 filoplumes of which there were two on one side and three on the 

 other all growing from the integument above the inner margin of 

 the quill base on either side. There were thus ten fully developed 

 coverts and a series of filaments that may be considered as the aborted 

 remnants of two more. Other filoplumes were not found nearer than 

 the lower part of the spinal tract above the oilgland. 



The humeral tract was three rows of papillae wide. In the wing 

 there were nine secondaries and ten primaries. The tenth (outer- 

 most) primary, while reduced in length and falcate in shape was 

 one-half the length of the ninth and was similar in form and relative 

 size to the tenth primary in the subgenus Vireo. The wing was 

 eutaxic. The ventral feather tracts beginning at the base of the bill 

 proceeded backward, broadened somewhat and then divided at a 

 point one-third of the total length of the neck above the shoulders. 

 After passing on to the breast these tracts expanded broadly, this 



