892 



SCIENCE 



[N. S. Vol. XXX. No. 781 



A remarkable disbovery of vertebrate fos- 

 sils in localities covered over by glacial drift 

 has recently been detailed by Professor Samuel 

 Calvin.° Two species of horses, five probos- 

 cidians, a camel, mylodon, megalonyx and 

 other extinct mammals are described. The 

 localities are not far from the Missouri River. 

 These remains v^ere buried in the soils belong- 

 ing to the Aftonian interglacial stage, which 

 preceded the Kansan ice sheet. Therefore, 

 they come to us from near the beginning of 

 the Glacial epoch. It is a fact which may be 

 noted here that, although a large part of Iowa 

 and a part of Kansas are covered by the 

 I^^ansan drift sheet, which offers facilities for 

 observation and which has been studied /ilosely 

 by geologists for many years, no bones or 

 teeth of fossil horses have yet, so far as I can 

 discover, been found on its surface. Nor have 

 any been found on the surface of the lowan 

 drift or in it. Nor are there any reliable 

 evidences that remains of horses have been 

 found in those regions that are occupied by 

 glacial deposits belonging to the early and the 

 late Wisconsin stages. 



The conclusion reached by the writer from 

 the data at hand is that horses became extinct 

 in the glaciated regions of North America, 

 and probably in the larger part or the whole of 

 the continent, about the middle of the Glacial 

 epoch, the Bond County, Bl., specimen being 

 the only one which indicates with some degree 

 of certainty the existence of the genus Equus 

 after the Illinoian stage. 



shorn' states that our knowledge of the 

 Lower Pleistocene is still confined to the west- 

 ern plains and mountains, while he regards 

 the fauna of the Port Kennedy cave, in Penn- 

 sylvania, as illustrating an early phase of the 

 mid-Pleistocene. Now, 80 per cent, of the 

 mammals of this cave belong to extinct spe- 

 cies. The Cromer Forest beds, arranged by 

 Osborn in the Pleistocene, by many authors, 

 as Geikie, Lapparent, etc., in the Pliocene, 

 contain, according to Clement Reid, 45 land 

 mammals, of which 21, or about 46 per cent., 



'Bull. Geol. Soc. Amer., Vol. 20, pp. 341-356, 

 pis. 16-27. 



' Bull. 361, p. 84. 



are extinct. We might, I think, with reason 

 hold that the mammals of the Port Kennedy 

 cave belong to the Pliocene. There seem to 

 be no good grounds for regarding them as 

 more recent than the fauna of the Equus beds 

 of the Great Plains. Calvin's discovery of the 

 mammals of the Aftonian seems to bring the 

 Equus beds up into the lower part of the 

 Glacial epoch, thus abolishing the Preglacial 

 stage. On the other hand, glaciation in North 

 America may have set in earlier than in Eu- 

 rope. Our Equus beds, though interglacial, 

 may nevertheless be also Pliocene. 



We may here consider the probable age of 

 the animals collected by Mr. Barnum Brown 

 in the Conard fissure, Newton County, Ark. 

 Mr. Brown has determined 51 species of mam- 

 mals, of which 24, or about 47 per cent., are 

 extinct, a ratio almost the same as in the case 

 of the land mammals of the Cromer Forest 

 beds. Evidently they belonged to a much 

 later time than those which perished in the 

 Port Kennedy cave. A few of the species 

 seem to indicate a mild climate ; most of them, 

 as the wapiti, the musk ox and several bur- 

 rowing species, show that the climate was 

 rather rigorous. Evidently some one of the 

 glacial ice sheets had pushed down boreal 

 forms into contact with those of a warmer 

 region. The Kansan ice sheet approached 

 within about 200 miles of the fissure. The 

 time of that sheet seems, however, too remote 

 that more than a moiety of the mammals 

 should yet be with us. It is more probable 

 that those remains were assembled in the fis- 

 sure^during the Illinoian stage. The horse 

 was yet in existence. The absence of the 

 large edentates may be due to their extinction 

 at that time or to their expulsion from the 

 region by the low temperature. The bones and 

 teeth of mammoths and mastodons, which cer- 

 tainly were in existence then, were probably 

 too large to be dragged into the fissure. 



There is space to consider only a few of the 

 other genera noted by Osborn. The genus 

 Cervus is put dovm as entering the country 

 late in mid-Pleistocene time. However, the 

 wapiti has been reported from a number of 

 localities, among them Big Bone Lick and the 



