356 NEW YORK STATE MUSEUM 



existing group was the type, and that all subsequent additions, 

 through discovery, of whatever rank they might be, were in a way 

 to be considered rather as aberrant forms. Thus it was that Cu- 

 culus, the common cuckoo of the Old World, was taken to be the 

 type of all the cuckoos, but we know better than this amounts to 

 now. Indeed, some of the strong osteological cuculine characters 

 are found to be rather feebly developed in Cuculus, as, for example, 

 the prominent lateral projection, on either side, of the ilium, over 

 the ilioischiatic foramen, and, too, the conspicuous prepubic spine. 

 These are manifestly cuculine skeletal characters, and they must 

 possess their significance, however ignorant we may be as to their 

 true meaning. Again, these two very characters are most conspicu- 

 ously developed in Geococcyx, but there is a good and sufficient 

 reason to account for the first mentioned one being there, for Geo- 

 coccyx is a marvelous runner, so the musculature of its pelvic limbs 

 is something extraordinary, and in order to afford attachment for 

 some of the more powerful of these muscles, the development of this 

 extra bony surface on the pelvis became necessary.^ But why this 

 particular character is to be found in various degrees of perfectness 

 in all other cuckoos is another matter. The tree cuckoos, for 

 example, possess it, and they are in no sense runners, in fact their 

 locomotory powers are markedly feeble, in this particular respect. 

 This likewise applies in the case of Crotophaga. Were the extinct, 

 ancestral cuckoos terrestrial forms, and the existing arboreal and 

 other species derived from them, and so still retain some of the 

 osteological characters of the ancestral stock, which characters are 

 now to be regarded in the light of vestigial ones? If so, Geococcyx 

 may be a modern, highly specialized representative of the prototype. 

 And, as Garrod thought, it may have some of the terrestrial galli- 

 naceous stock in its composition, or rather organization. Here is 

 where the zygodactylous Musophagidae would come in, and the 

 gallinaceous ancestral line is one of enormous antiquity, and at 

 least one related group, the tinamous, still retain in their skeletal 

 structure characters of the reptiloid kind, which were present in the 

 earliest forms of birds, now long extinct. 



Further on this line, I now hardly feel prepared to venture, 

 and certainly not until I have morphologically examined a far 



1 Shufeldt, R. W. Contributions to the Anatomy of Geococcyx californianus. Zool. 

 Soc. Lond. Proc. Nov. 1886. p. 466-91, pi. 42-45- Also, A Review of the Muscles 

 Used in the Classification of Birds. Jour. Comp. Med. & Surg. New York. Oct. 1887. 

 Reprint p. 1-24, fig. 1-13. Several of the natural size figures present the myology 

 of the pelvic limb of the Ground cuckoo (Geoc.occy.x californianus) of 

 the United States avitauna. 



