DISCUSSION AND CORRESPONDENCE.

A RECENT PALEONTOLOGICAL INDUCTION.

    THE concept of arboreal 'horses' already thrice discussed in the current volume of SCIENCE, or even concepts of fabled Pegasi, are, from a philosophical standpoint, rational and legitimate products of human

466                        SCIENCE              N.S. Vol. XX, No. 510.

consciousness. Nevertheless, the probability of such

conceptions having had real counterparts in the material world is absolutely nil, so far as experience shows, and for like reason we can ascribe only a mythical existence in times past to warm-blooded reptiles, feathered reptiles, or reptiles possessing so eminently bird-like a characteristic as the gizzard.

    It is, therefore, surprising to find a writer in SCIENCE (No. 501, p. 185) advancing the anomalous conception of reptiles with organs corresponding to the avian gizzard. The solitary fact upon which Mr. Barnum Brown bases his conclusion is the discovery, in a number of instances, of small-sized silicious [sic] pebbles in association with plesiosaur skeletons from the western Cretaceous. Certain corollary  assumptions, apparently accepted as axiomatic by Mr. Brown, but nevertheless debatable, may be stated as follows:

    (1) These' stomach stones' were contained within the alimentary canal prior to the death of the creatures, and not accidentally deposited upon or with their remains. (2) The stones were intentionally swallowed, and not taken promiscuously with other fare, as might happen in bottom-feeding. (3) They served as a mechanical aid to digestion through the intervention of a supposititious gizzard-like organ. (4) Thin-shelled prey like cephalopods could not have been crushed upon one another without the admixture of a judicious quantity of' stomach stones. (5) The non-occurrence of such stones amongst European reptiles proves only that the latter' had no stomach' for them, not that they were gizzardless. (6) The history of the gizzard (horresco referens) shows that it was developed first amongst cold-blooded vertebrates, then lost by them, and afterwards independently acquired by birds. Incidentally it appears that plesiosaurs possessed the most highly specialized digestive apparatus known amongst reptiles, ancient or modern.

     For our part, begging pardon of Mr. Brown, we are willing to consign to birds the exclusive enjoyment of gizzards and feathers. A cogent reason for suspending judgment as to the function of 'stomach stones' is found in their limited distribution. Before asking us to believe that all plesiosaurs had 'gizzard- like arrangements' [sic], let it be shown that all plesiosaurs and related reptiles had the habit of gorging themselves with foreign matter to the extent asserted of American species, and let no doubt remain that these pebbles are not of adventitious origin.

                                                          C. R. EASTMAN.

HARVARD UNIVERSITY.