iSS6. 



Lucas on the Affinities of Chcstura. 447 



The free caudals of TrocJiihis and ChceUtra agree in having long, 

 slender, recurved transverse processes, in which particular they 

 resemble the Goatsuckers, and contrast with the Swallows, whose 

 short transverse processes are like those of other Passeres. 



A character of great importance is found in the manner in which 

 the ribs join the sternum. In Trochihts and Chcctnra they 

 articulate with the body of the sternum, while in Chelidon^ as in 

 all Passeres I have examined, the ribs are attached only to the 

 costal process. In this particular, as in many others, the Goat- 

 suckers more nearly resemble the passerine birds than does 

 Chcetura. To say nothing of the great depth of keel* possessed 

 by both Trochihis and Chcetura^ their sterna agree in having 

 small costal processes and un-notched, rounded posterior borders. 

 In C/io'.tura, as Dr. Shufeldt has noticed in Paiiyptila^ there are 

 numerous vacuities in thebody of the sternum and the upper part 

 of the keel. This is but an exaggeration of the structure found 

 in Trochilns^ whose sterninn is honey-combed by irregular 

 depressions which in many places lack but little of completely 

 perforating the walls of the sternum. 



The manubrium is entirely wanting in Trochihis and very small 

 in Chcetura. 



In all these particulars Chcetura and Trochihis contrast 

 strongly with CheUdojt. which has the large Y-shaped manubrium, 

 prominent costal processes, and deeply bi-notched sternum so 

 characteristic of the Passerines. t The sterna of Chordeiles and 



* Speaking of /'a//);;>///a, Dr. Shufeldt says (p. 907) "the keel to the sternum is not 

 so deep in comparison with the remainder of the bone as we often find it among Pas- 

 seres, and in this particular it is not to be mentioned with the extraordinary carinal 

 development of Trockilusy 



Dr. Shufeldt's eye has certainly deceived him here, for a pair of dividers applied to 

 his figures shows that the proportion of length to depth is very nearly the same in both. 

 As to the matter of carina! development among the Passeres, I must confess myself 

 unable to name one which at all equals Chcztura or Panyptila. At the same time it 

 must be borne in mind that these proportions do not show the true state of the case, 

 since Tro'chilus and Cluztura have sterna not only unusually deep but unusually long. 

 The relation of depth to length is much greater in the sternum of Ckordei/es than in 

 Trochihis, but the breast bone of Chm-deilcs is a short one. In ChcEtura and Campy- 

 lopterus the proportion of length to depth is identical. 



t Among birds the characters aftbrded by the sternum are so important that I must 

 confess myself a little surprised that Dr. Shufeldt should so readily reject them (see p. 

 914), when only two pages before he lays stress on the development of the phalanges. 

 The notched or un-notched condition of the xiphoid border is in no way due to physi- 

 ological adaptation, while the modifications of the phalanges are very largely so caused. 

 Some of the parrots fly well, some very poorly, none at all compare with Trochihis or 

 Chcetura, And yet all {fide Huxley) have the sternum un-notched. 



