2 1 8 Correspondence. [April 



the side as a sliarp-pointed and handsome hook (see also Fig. i), termi- 

 nating in a free extremity. Figure 4 shows this arrangement to be quite 

 difterent in Sfhyrapicus, where the form of the external branch is nar- 

 rower, and tiie bifurcation higher up towards the neck of the bird. It too, 

 however, terininates in a free-pointed extremity at the side. The abdom- 

 inal part of the main ventral tract is much stronger in Sfhyraficus than 

 it is in Harris's Woodpecker, in which latter species it usually dwindles 

 to a single row of contour-feathers before arriving at the vent. Both 

 species have the apertui-e of the vent completely surrounded by a single 

 row of small contour-feathers, while in Dryobates theve are posterior to 

 this region a mid-coccygeal pteryla, with an oblique lateral one on each 

 side of it (Fig. 3). These I have designated as the 'postventral tracts.' 



Colaptes has, both in arrangement and form, its ventral and postventral 

 tracts almost identically the same as we find them in the genus Dryobates. 



Nitzsch, alluding to the rectrices and remiges in the Woodpeckers, 

 says ''twelve tail-feathers, but the two outer ones small and bent in be- 

 tween the two preceding ones," and "the wings bear from nineteen to 

 twenty-one remiges, but always ten on the pinion, of which the first is 

 rather short, the second is likewise shorter than the following ones, but 

 the third is sometimes equal to the fourth and fifth, and with them the 

 longest, and sometimes exceeded by the fourth, fifth and sixth, which are 

 then of equal length." 



Persons interested in the study of this subject may well consult besides 

 Nitzsch's 'Pterylography' certain important papers in the early issues of 

 the 'Proceedings' of the Zoological Society of London. 

 Faithfully yours. 



Fort Wingaie, New Mexico, 

 2 1 St Feb. 18S8. 



R. W. Shufeldt. 



Polydactylism in Birds. 



To THE Editors of the Auk : — 



Sirs: — My attention has been directed to a short article in 'The Auk' 

 (Vol. IV, No. 4, pp. 331-333, Oct. 18S7), on 'Ornithological Curiosities. — 

 A Hawk with nine toes, and a Bobolink with spurs on its wings.' I do 

 not profess to be an ornithologist, though much interested in the subject, 

 and something of an observer of bird life; I prepare this note as a teratol- 

 ogist. I am much pleased with the report of the cases of the supernu- 

 merary development by Mr. Henry K. Coale, and hope his example will 

 be followed by others from numerous observers all over the land. 



In my soinewhat extensive researches for the purpose of collecting and 

 classifying the bibliography and references relating to the 'The Material 

 of Teratology,' I have been surprised at the infrequency as well as the 

 meagreness of reports, and the almost absence of even incidental inen- 

 tion of casf^s of supernumerary and duplex development in birds. Such as 



