1882.] PTERYLOSIS OF MESITES. 269 



being of a furcate form, with the united part about 1 inch long, and 

 inclosing a fairly broad median space. The limbs of this posterior 

 fork are strongly dilated in the middle part of their extent, being there 

 6 to 7 feathers broad, and united externally by scattered feathers with 

 the very broad and long lumbar tracts, which are arranged in about 

 six rows of not closely -placed feathers, the posterior row of these 

 being considerably the stronger. 



The humeral tracts are not very broad or strong, and are quite 

 distinct, anteriorly, from the inferior tract. 



This last, which (as already described) commences on each side 

 about halfway down the neck, springing at once independently 

 from the continuous feathering of the anterior cervical region, 

 ceases altogether at the commencement of the pectoral region 

 (extending as far as the most anterior of the ventral powder-down 

 patches to be presently described). It recommences, however, a little 

 lower down as a very narrow tract, composed at first of only single 

 feathers, but subsequently becoming stronger and broader (though 

 even here only two feathers broad), in which condition it runs on, as 

 the main inferior tract, to terminate near the vent. 



Strange to say, what must be considered the equivalent of the 

 outer pectoral branch of ordinary birds is here quite free throughout 

 from the main stem, with which it is not even united anteriorly, 

 where it is separated by the already-mentioned powder-down patch, 

 whilst posteriorly it runs parallel to, but quite free from, the main 

 stem. 



The powder-down patches of Mesites resemble those of the 

 Ardeidce, of Leptosoma, and Podargus in their compactness, as well 

 as in the definiteness of their areas, as opposed to the more scattered 

 and diffused forms they present in Rhinochetus, Eurypyga, Cryp- 

 turus, and other birds. But in their exact distribution they differ 

 materially from any of these. 



As already described by Mr. E. Bartlett, there are five pairs ' of 

 powder- patches in Mesites. Of these two pairs are dorsal, two 

 ventral, and one lateral in position. All have the form of well- 

 defined more or less oval areas, covered by a dense mat of closely 

 aggregated long powder-down plumes. 



The most anterior pair is placed close to the median line, the 

 patches being only slightly separated from each other, at the com- 

 mencement (apparently) of the interscapular region and inclosed 

 between the two dorsal tracts, a little before these pass into their 

 weaker posterior fork. 



The second dorsal patch is situated on the rump, close to and just 

 outside the terminal part of the dorsal tract, between that and the 

 posterior termination of the lumbar tracts of each side. 



• In the Ardeidce the number varies from one pair (Baleeniceps) to four pairs 

 {Cancroma). Three is the most ordinary number. The presence of a single 

 caecum in Balcsniceps (as fortunately demonstrated by a preparation mounted 

 in. the Museum of the Royal College of Surgeons), together with these powder- 

 down patches, renders its Ardeine nature nearly certain, as already suggested 

 by Mr. A. D. Bartlett (P. Z. S. 1861, p. 131). 



