Mr. P. R. Lowe on the Crab-Plover. 321 



cantUus of the eye. Geueral shape of bill unlike that ol: 

 adult — more typically pluvialiue. Inside of mouth pale 

 yellow; tongue without spots or markings. 



Feet and legs. Slaty blue ; scaling of podotheca exactly 

 similar to that of the adult ; webbing as in the adult. 



Pterylosis. 



The accompanying drawing (text-figure 8) depicts the 

 feather-tracts of a young Crab-Plover a few days old, as 

 viewed from the dorsal aspect. Beyond calling attention 

 to the strength of the crural tract, which is sufficiently 

 obvious in the figure, a detailed description seems un- 

 necessary. 



A drawing which I made of the feather-tracts of the 

 adult Crab-Plover, so kindly sent to me by Dr. Brockman, is 

 practically identical in detail with the figure of the young 

 Crab-Plover here reproduced, but the feathers of the anterior 

 dorsal tract are degenerate from the vertex of the skull 

 backwards to a point about an inch distad of the bifurcation 

 of the tract in the interscapular region. From this point to 

 the termination of each bifurcation the spinal tract is very 

 strong. The crural tract in the adult is also conspicuously 

 strong and in marked contrast to the degenerate feathers of 

 the posterior portion of the dorsal tract. This posterior 

 portion of the dorsal tract, or to give it the name which I 

 employed in the description of the pterylosis of the embryo 

 Sheath-bill (c/. ' Ibis,' Jan. 1916, p. 130)— the dorsi-sacral 

 tract, — is separated from the anterior portion by a distinct 

 break in the feathering of both the young and adult bird 

 {cf. text-figure 8), and its anterior extremity is not bifurcated, 

 not even narrowly, as it is in the case of the Sheath-bill 

 {cf. 'Ibis,' 1916, p. 131, text-figure 1). In an adult 

 specimen of Larus argentatus, whose feather-tracts I have 

 carefully examined and drawn, this posterior portion of the 

 spinal tract (dorsi-sacral) is very deeply and conspicuously 

 cleft. The same condition of things obtained in some young 

 chicks of the Common Tern which I examined. Moreover, 

 in these young Terns the dorsi-sacral tract was quite strong 



SER. X. — VOL. IV. Y 



