1916] Chandler: Structure of Feathers 309 



cilia, subequal in size. On more distal portion of barbs, sharp 

 distinction between base and pennulum is lost, the barbules becom- 

 ing very narrow and simple, with a few weak, curved ventral cilia 

 near tip. Proximal barbules very much like those of back, but 

 more simple, and on terminal portion of barbs assuming a form very 

 similar to distals opposite them, except that the ventral barbicels are 

 longer and more numerous. 



h) Other Types . 

 (1) Plotinae 



Plot us, although grouped with the Phalacocoracidae, constituting 

 the subfamily Plotinae, differs from Phalacocorax so widely in its 

 feather structure that on this basis alone it should be entitled to 

 full family rank. The Steganopodes as a group are characterized 

 by the unusual difference in the different families as regards their 

 minute feather structure, but no two families of the order are more 

 distinct from each other than is Plotus from Phalacocorax. 



Taking Plotus anhinga as a type, we find that the distal bar- 

 bules of the inner vanes of the remiges (pi. 18, fig. 13a) are remark- 

 ably reminiscent of those of the Cathartidae. The bases are elongate 

 and narrow, about 0.35 by 0.03 mm., while the pennula are about 

 0.45 mm. long. The twist between the base and pennulum is of 

 such a nature as to give the dorsal contour a peculiar, characteristic 

 wavy curve. When spread back between thumb and forefinger 

 both the base and the tip of the pennulum lie in a vertical plane, 

 only the moderately broad booklet area lying on its side, giving it 

 a hump-backed appearance. The ventral teeth are lobate, and pro- 

 ject straight forward in a direct line with the ventral edge of the 

 base. The booklets, usually five in number, are relatively short 

 and stout, but progressively increasing in length ; the ventral cilia 

 are coarse, straight, and blunt, all but the proximal one or two 

 being closely appressed to the barbules. All of the dorsal barbules 

 are absent entirely, except the specialized one or two basal ones, 

 which have the form of stout, blunt, forward and laterally project- 

 ing spines. Immediately distal to them the dorsal contour of the 

 barbule curves evenly downward. The proximal barbules (pi. 18, 

 fig. 13&) are hardly less peculiar. In these the base is short and 

 stout, hardly longer than the base of the distals, and about 0.55 

 wide, with very short, triangular ventral teeth. The pennulum is 

 remarkably short and stout, being considerably shorter than the 

 abbreviated base, and 0.02 mm. wide, the cells of the ventral tooth 

 region and beyond having conspicuous, recurved dorsal spines, and 



