38 Notices of 3Iemoirs — Prof. 0. C. Marsh on S'esperorms. 



depression of base-level in New England reached 2,700 feet at least. 

 As there was a Mid-Pliocene (our separation of Pliocene and 

 Pleistocene formations being largely ai'bitrary) elevation of unde- 

 termined amount, and as there have been several minor oscillations 

 of level of land and sea, there is great latitude in the application 

 of the phenomena to the Glacial epoch not j^et determined — only 

 that great elevation of measurable amount did obtain in Pleisto- 

 cene days. With alternations of elevation between the North 

 Atlantic and American plateaux, the changes of currents would 

 further modify the climatic conditions of the period, so that this 

 paper only suggests one phase of physical changes — tending to 

 produce the phenomena of the Glacial period. 



isTOTiciES OIF nycEnvnoiias, 



I. — The Affinities of Hesperornis} By 0. C. Marsh. 



IN the autumn of 1870, I discovered in the Cretaceous of Western 

 Kansas the remains of a very large swimming bird, which in 

 many respects is the most interesting member of the class hitherto 

 found, living or extinct. During the following year, other specimens 

 were obtained in the same region, and one of them, a nearly perfect 

 skeleton, I named Hesperornis regalis.'^ In subsequent careful 

 researches, extending over several years, I secured various other 

 specimens in fine preservation, from the same horizon and the 

 same general region, and thus was enabled to make a sj'stematio 

 investigation of the structure and affinities of the remarkable group 

 of birds of which Hesperornis is the type. The results of this and 

 other researches were brought together in 1880, in an illustrated' 

 monograph.^ 



In the concluding chapter on Hesperornis, I discussed the affinities 

 of this genus, based upon a careful study of all the known remains. 

 Especial attention was devoted to the skull and scapular arch, which 

 showed struthious features, and these were duly weighed against the 

 more apparent characters of the hind limbs, that strongly resembled 

 those of modern diving birds, thus suggesting a near relationship to 

 this group, of which Colymhus is a type. In summing up the case, 

 1 decided in favour of the ostrich features, and recorded this opinion 

 as follows: — 



" The struthious characters seen in Hesperornis should probably 

 be regai-ded as evidence of real affinity, and in this case' Hesperornis 

 would be essentially a carnivorous, swimming ostrich." ("Odontor- 

 nithes," p. 114.) 



This conclusion, a result of nearly ten years' exploration and 

 study, based upon a large number of very perfect specimens and 

 a comparison with many recent and extinct birds, did not meet with 



^ From the American Journal of Science, vol. iii, 1897. 



2 Sillimau's Journal, vol. iii, p 56, January ; and p. 360, May, 1872. 



3 " Odontoruithes : a Monograph on the Extinct Toothed Birds of North 

 America." 4to, 34 plates ; Washington, 18i;0. 



