360 University of California Publications in Zoology [Vol. 11 



From the umbilicus, in the position of the aftershaft, and un- 

 doubtedly representing it, are ten or twelve short, spreading 

 barbs, with numerous appressed awl-shaped barbules. The barbs 

 are about 0.6 millimeter in length, and the barbules 0.2 milli- 

 meter. It is interesting to note that in many birds which are 

 devoid of aftershafts the eyelashes are entirely without barbs. 



Pycraft (1910) remarks that the eyelashes of many birds, 

 e.g., ostriches and hornbills, are akin to filoplumes. Certainly 

 in the case of hawks the eyelashes have no relation whatever to 

 filoplumes, as they are very evidently modified contour feathers. 

 The steps in their reduction from ordinary contour feathers may 

 be seen in the ear coverts and postorbital bristles, in which they 

 show very plainly the method of their evolution. The ear coverts 

 could never be mistaken for anything but modified contour 

 feathers ; the postorbitals differ from these only in the further 

 reduction of barbs and barbules, leaving the terminal portion of 

 the shaft as a stiff black bristle ; and the eyelashes differ from 

 the po.storbitals only in the complete loss of the few remaining 

 barbs attached to the shaft. 



Loral and Rictal Bristles 



Filling in the space between the eye and the beak are some 

 very numerous and closely inserted feathers known as loral 

 bristles. They are of the same type as the eyelashes, the only 

 difference being in the sharp upward curvature, resulting in the 

 tips of the bristles almost meeting over the beak, and partly 

 covering the nostrils. The loral bristles are radially arranged 

 around a point a short distance in front of the eye, so that the 

 front upper ones are considerably longer than the others, some 

 of the bristles being nearly fifteen millimeters long. 



Filling in the space between the two rami of the lower 

 mandible in a manner similar to that of the bristles in the loral 

 region are the rictal bristles, which are numerous and closely 

 inserted. They are of two types, those immediately behind the 

 symphysis of the jaw being of the eyelash type, i.e., with a naked 

 shaft, and a few barbs representing the aftershaft, while the 



