July 7, 1910] 



NATURE 



13 



struction are based, so that each may judge of the 

 extent to which it is trustworthy. 



Perhaps the most interesting real novehy is a small 

 skeleton from the Middle Eocene of Wyoming, deter- 

 mined by Prof. Osborn to belong to a primitive 

 armadillo. Fragments of this animal were obtained 

 some vears ago by Dr. J. L. Wortman, and ascribed 

 by him to a Lemuroid under the name of Meta- 

 cheiromys. Four good specimens now seem to show 

 that it is truly an armadillo, differing chiefly from the 

 typical existing armadillos in "the probable presence 

 of a leathery instead of a bony shield, of an enamel 

 covering on the single large caniniform teeth in the 

 upper and lower jaws and the degeneration of other 

 teeth." This discovery confirms the suppositions of 

 Marsh, Wortman, and Schlosser as to the existence 

 of Edentata in North .'\merica in the Eocene period; 



jm. 



1 of Tyra. 



and it adds to the difficulties of understanding the 

 earlv Tertiary mammal faunas of South .\merica. 



."Vnother astonishing discovery is that of a colossal 

 carnivorous Dinosaur, Tyrannosaurus (Fig. 2), from 

 the Upper Cretaceous (Laramie formation) of Wyo- 

 ming and Montana. It has hitherto been supposed that 

 the flesh-eaters were all much smaller than the 

 largest vegetable-feeders among Dinosaurs ; but here 

 is a reptile like Megalosaurus, with a skull from 

 4 to 5 feet in length, and when standing on its heavy 

 hindquarters reaching a height of from 16 to 17 feet. 

 .Another new herbivorous Dinosaur, Ankylosaurus, 

 from the same geological formation, measures 14 feet 

 in length, and is armoured like the South American 

 Glyptodons. 



The technical papers on remains of horses and 

 rhinoceroses, by Prof. Osborn and others, and on 

 camels and deer, by Dr. Matthew, are of extreme 

 scientific value. The discussion of the extinct horses 

 is especially exhaustive, and the result is that it be- 

 comes impossible at present to recognise any exact 

 genetic series. Mr. Gidley even remarks that "there 

 is a considerable phvletic hiatus between the groups 

 of the Equidae, which are as yet not bridged over by 

 intermediate forms " ; and he adds that this hiatus is 

 particularlv marked between the .Anchitherium-group 

 and the Protohippus-g/'oup, which " greatly overlap 

 each other in time." Dr. Matthew's explanation of 

 most of our difficulties in understanding the evolution 

 of the European and North American Tertiary mam- 

 malia is that northern .Asia was their actual ])lace 



NO. 2123, VOL. 84] 



of origin. He thinks that "in Europe, on one sidt 

 of this centre, in America, on the other side, we 

 have parallel series of approximate phylogenies ; 

 sometimes closer in the one country, sometimes in the 

 other." Until the early Tertiary manmialia of 

 northern Asia are discovered, we cannot advance 

 much further towards real origins. 



Prof. Osborn and his associates are indeed to be 

 congratulated on the wide import of the work they 

 have done, and the excellent manner in which it is 

 published. We would commend it to the notice of 

 all students of biology. k. S. W. 



EXPERIMENTS ON AIR RESISTANCE. 



IN La Nature (February 26) there is a description 

 by M. Fournier of the new laboratory which M. 

 Eiffel recently erected for the purpose of carrying 

 out his researches on the air resistance of plates and 

 models, more especially with reference to the solution 

 of problems in aeronautics. 



It will be remembered that M. Eiffel's earlier 

 experiments were made on plates and models let fall 

 from the second stage of the Eiffel Tower. The 

 general agreement of his results on flat plates with 

 those obtained by Mr. Dines on a whirling table and 

 those at the National Physical Laboratory in a cur- 

 rent of air was shown in the curves 

 illustrating the present writer's article on 

 the subject of wind pressure in Nature 

 of May 28, 1908. As this method was 

 not suitable for the rapid determination 

 of centres of pressure, and the "lift" 

 and "drift" of inclined plates, M. Eiffel 

 has now commenced experiments in a 

 current of air, and 

 the manner in 

 which this current 

 is maintained pre- 

 sents some novel 

 'and interesting 

 features. Hitherto, 

 experiments by 

 this method have 

 carried out by suspending the models 

 long channel with parallel sides through 

 which air was drawn by means of a fan. This 

 arrangement is open to two objections — (i) the diffi- 

 culty of maintaining the velocity of the current 

 uniform across the channel, and (2) the limited size 

 of the models which could he used without an appre- 



of Natural Hislory. 



been 



ciable effect on the resistance due to the walls of the 

 channel. The first difficulty is overcome by introduc- 

 ing resistances to the flow where necessary, which is 

 a long and tedious process, and the second by limiting 

 the size of the models to within two or three per cent, 

 of the area of the channel. The novelty of M. Eiffel's 

 method consists in his using a comparatively short 

 channel, and in suspending his models in a closed 



