Apart from the Owls above noted, this bone has been found in Otogyps calvus, Heterospizias meridionalis, Buteo melanoleucus, B. pennsylvanicus, B. lineatus, Circus gouldi, Asturina pucherani, and Haliæetus albicilla.
A. Os prominens of Otogyps calvus, full size.
B. Os prominens of Bubo virginianus, seen from above to show articulation with radius, full size.
It is absent in Polyborus tharus, Milvago chimango, and the following peculiar forms which were examined to see if they would throw any light upon the subject: Nyctibius, Strigops, Nestor, Megapodius, Ocydromus, and Atagen. Neither was any trace of it to be found in two specimens of Pandion haliæetus from N. Africa and the Duke of York group. Dr. Shufeldt’s theory that the os prominens is for the purpose of extending the wing area struck me, as it did Mr. Jeffries, as being untenable, from the fact that the increase of surface thus obtained was too slight to be of any value.[[48]]
The first proposition of Mr. Jeffries’ summary is that the bone serves to keep the friction of the extensor patagii longus from the carpus. Were this the case it ought surely to be present in the Albatross and Gull, birds which in a fresh breeze are continually flexing and extending their wings according to the direction of their flight and the varying force of the wind. But in both these birds the os prominens is absent,[[49]] and moreover, as we see in the Owls, it may be so situated as not to prevent the friction of the ulnar portion of the tendon. Second, that it serves only to a limited extent to increase the power of the extensor patagii longus to abduct the thumb, is shown by the fact that in the majority of cases that tendon is inserted in the first metacarpal. The exceptions to this, so far observed by me, are in Otogyps calvus and Haliæetus albicilla, where there is a strong tendon running from the os prominens to the first phalanx of the thumb. The third proposition has already been considered, and the fourth (that it protects the carpus) must be rejected, both for the reason given by Mr. Jeffries, and because as we see it in Owls it frequently does not lie over the carpus at all. Only in Otogyps calvus does the os prominens seem to exist as a simple sesamoid, and in that bird it is imbedded in the tendon of the extensor patagii longus, and glides over the scapho-lunar. Were I to venture a suggestion it would be that by its serving as a point of attachment for the tensor patagii longus, that tendon is freed from all duties save that of “puckering up” the anterior margin of the wing; but, as stated before, that theory is by no means entirely satisfactory to me.
A LIST OF BIRDS FROM THE LOWER MISSISSIPPI VALLEY, OBSERVED DURING THE SUMMER OF 1881, WITH BRIEF NOTES.
BY O. P. HAY.
During the summer of 1881 the writer and two companions spent a little more than a month in the South, especially in the State of Mississippi, travelling and studying its zoölogy. Our primary object was to collect fresh water fishes; and to this we devoted the greater part of our time and efforts. Incidentally, however, we collected and made observations on other animals. Hence this list of birds and the few notes concerning them. I did not intend to publish this list until I had opportunity to make additions to it; but the recent publication by Dr. F. W. Langdon of his field notes on birds observed by him, early in the spring, at a point a little farther south, has made it seem proper that I should contribute my little toward making known the ornithology of this region.
Our observations and collections were made of course under difficulties, and no attempt was made to secure nests and eggs, or, in any special manner, notes on the breeding habits of birds. Still, on account of the season when our trip was made, this list may be of some value as indicating that the birds observed are summer residents. The number of species recorded is not large, but I include only birds that I am reasonably sure were seen. In nearly all cases the birds were shot, and identified by means of descriptions. Others were seen, but as they were not identified with certainty, they are not included in the list.
The birds noted as found at Memphis, Tenn., were really seen in Arkansas just across the river from Memphis. Most of our other notes were obtained at Vicksburg and Jackson, Miss.