OSTEOLOGY OF BIRDS 355 



ural genera of cuckoos. In a brief paper, like the present, these 

 have been contrasted with sufficient conciseness in foregoing para- 

 graphs, as to render it unnecessary to present them in a form of a 

 table in this place. By way of recapitulation, however, it may be 

 as well to invite attention once more to the differences exhibited 

 on the part of the foramen magnum and the crotaphite fossae in the 

 skulls ; the number of vertebrae in the spinal column ; the form of 

 the sternum and its xiphoidal extremity; the sternal articulation 

 of the hypoclcidium of the os fnrcula; the marked differences in 

 the proportions of the respective bones of the pectoral and pelvic 

 limbs; and the very decided morphological differences in the two 

 pelves. 



Having now carefully examined and compared the skeletons of a 

 Coccystes and a Cuculus, and recompared the characters they ex- 

 hibit with the corresponding ones as I found them presented on 

 the part of the skeletons of various other kinds of cuckoos de- 

 scribed in my previous memoir on the subject, published by the 

 American Philosophical Society of Philadelphia, I find myself not 

 much better prepared to offer an opinion upon the natural, or 

 rather true, relationships of the Coccyges to other avian groups, 

 than I was before I made the researches of which an account is 

 given in the present contribution. Still something has been gained, 

 a little progress made, and every ray of light of the kind, morpho- 

 logical illumination as it were, is sure to bring the taxonomer and 

 the student of comparative osteology just so much nearer the goal. 



It is still a problem to be solved where the cuculine stock first 

 commenced in time to branch off from the " avian tree," and still 

 more of a problem what those birds looked like, and what char- 

 acters they exhibited in their skeletons. We have no such informa- 

 tion as this, and may never have it, and this being the case it be- 

 comes a matter of the greatest difficulty to decide which species 

 or genus of cuckoos is now most nearly related, morphologically, 

 to the pristine ancestral birds. 



Was it a ground cuckoo or a tree cuckoo? Were they big or 

 little forms? Along the line, where did the reversion of the fourth 

 toe first become established, and what caused it? That this latter 

 has but scant classificatory significance now, there is hardly any 

 question, though did we but really know why a woodpecker, and 

 a cuckoo, and a touracou all possess zygodactyle feet, it might be 

 of very considerable assistance. The old-time classifiers of birds 

 were often possessed of the idea that the common form of the 



