RIC OF T R L HI TOR Th Evolution of tl Horse
B • \i\ i Il ia n1 . • 11at th ,~ , F h . D.
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VOL. 111 , o. I J ~y, I 0 , uid I afl t , o. < American Museum of Natural History,,
Officers. President, MORRIS K. JESUP. First Vice-President, Second Vice-President, WILLIAM E. DODGE. HENRY F. OSBORN. Treasurer, Director, CHARLES LANIER. HERMON C. BUMPUS. Secretary and Assistant Treasurer, JOHN H. WINSER.
Scientific Staff. Director, HERMON C. BUMPUS.
Department of Public Instruction. Prof. ALBERT S. BICKMORE, Curator. Department of Geology and Invertebrate Palreontology. Prof. R. P. vVHITFIELD, Curator. EDMUND 0. HovEY, Ph.D., Associate Curator. Department of Mammalogy and Ornithology. Prof. J. A. ALLEN, Curator. FRANK M. CHAPl\IAN, Associate Curator. Department of Vertebrate Palreontology. Prof. HE RY FAIRFIELD Os BORN, Curator. W. D. MATTHEW, Ph.D., Associate Curator. 0. P. HAY, Ph.D., Assistant Curator. Del--'artment of Entomology. WILLIAM BEUTENMVLLER, Curator. Departments of ·Mineralogy and Conchology. L. P. GRATACAP, A.M., Curator. Department of Invertebrate Zoology. Prof. HERMON C. BUMPUS, Curator. GEORGE H. SHERWOOD, A.M., Assistant Curator. Department of Anthropology. Prof. FREDERIC "\V. PUTNAM, Curator. Prof. FRANZ BoAs, Curator of Ethnology. MARSHALL H. SA VILLE, Curator of Mexican and Central American Archreology. HARLAN I. SMITH, Assistant Curator of Archreology. Library. A. WOODWARD, Ph.D., Librarian.
,;;~ or A.::, E OF MAMMALS. AGE OF MAN. l~EPTILE L~ T" MATl: ; ,<): 0 Vt_,ARS E5TIMATCO AT 50,000 Yl:Al!S
PLEISTOCENE MODERN
Pl~1,to,tnt Horse, h.J.'H o,,, Toe on e.ieh Foot h.t'lf' C1\t.i ------~Mod,rn Hl)f"5n One Toe or r PLIOCENE 51,)mt Pho1..tnr Hor,u hJ•t Thre,, Tou.othtrJ h4vt Oiit Tot on t.ach Foot
MIOCENE P11hou•• Hor u• ·,.1_w-, Th,., Tou • tadl fQ{)lf. Th, -;,.;, Ton .u 09• l'ludl tllt 6ro••d
OL(GOCENE 01,go,-,~u !oh ttO iJ 1wo Thtff THI on NtN Fl)o~ Tht 5 1It loa, l•u•~ ,.i., 6r>o·1d
EOCENE Eoc.-,,.H,~.t'l'1bi..it~·ovf Toh ..,o .. f-sli•t J:' Th,• T'c-•1 tn rr., M,,id :_. RETACIC
i'lm EVOLUTION OF THE HORSE. FEET Series on exhibition in the American Museum LLL' '[l .\'ll )l l·\" LL""l[()_" \.lo.·c, I,(' LL ~L\i\BL\L . . l.- 'lllE II R .. E. BY\\. I . ;\l \TTlll:.W, Ph.I ., 'ur. r, J 'I. rtmcnt f Yert ·l rat Pabonlol uy . •\. ~ cl m ·ti ~ nimal t.h I wh · th" · m .. n an li\~ . II · v r th ,,. rl h · n t R man \\ h n I yrr h u an 1 hi ( 1 r k 1 nt _ .. th 'r h- ·haki·1u l 'L t, - > fi rh , 11 > h r an i m · · li i 1 1 t f L · I -.- ·11 1 • ' 4 EVOLUTION OF THE HORSE bones, one on each side, called splint-bones. These represent the second and fourth digits of other animals, but they do not show on the surface, and there is nothing like a separate toe. So that the horse may be said to be an animal that walks on its middle finger-nail, all the other fingers having disappeared. The teeth of the horse are almost equally peculiar. The molars are long, square prisms which grow up from the gums as fast as they wear off on the crowns. Their grinding surface exhibits a peculiar and complicated pattern of edges of hard enamel between which are softer spaces composed of dentine and of a material called '' cement,'' much like the dentine in quality but formed in a different way. The dentine is formed on the in side surfaces of the enamel while the tooth is still within the jaw bone; the cement is deposited on the outside surfaces of the enamel after the tooth has broken through the jaw-bone and before it appears above the gums. Various other peculiarities distinguish the Horse from most other animals ; some of these are shared by other hoofed animals. The two long bones of the fore-arm (radius and ulna) are separ.a te in the greater number of animals, but in the Horse, and in many other hoofed animals they are consolidated into a single bone. The same consolidation is seen in the bones of the lower leg (tibia and fibula). The lengthening of the foot and stepping on the end of the toe raises the heel in the Horse, as in many other animals, to a considerable height above the ground, where it forms the hock joint, bending backward, as the knee bends forward. In these as in various other ways the legs of the horse are especially fitted for swift running over hard and level ground, just as its teeth are for grinding the wiry grasses which grow on the open plain. The Zebra and the Ass have the same peculiar structure of teeth and feet as the Domestic Horse, and differ only in the color of the skin, proportions of various parts of the body etc. FOSSIL HORSES OF THE AGE OF MAN. The Age of Man, or Quaternary Period, is the last and by far the shortest of the great divisions of geological time. It includes the Great Ice Age or Glacial epoch (Pleistocene), when heavy en ~ r -I 0 z 0 : 0 C C ::: c.o 0 0 - -i ::.. j - - ::0 ., 0 - ~ -· :I: r - 0 f ~ :::0 - ,, ~ 0 0 z 0 -I X > EVOLUTION OF THE HOR E 7 ~ ntin nt 1 ~la 1 rs l1l rth rn part ul I., un >p · and . ·, 1·th .\m ri \1.: n l th Pc· nt l'..pu ·h. of rn<>r · m ,d rat· lima ' lurin~ whi ·h '1\·ifonti m ha: aris n. I 1 h · rl_· part f th (juat rnar~ P ·ric l \\ ild s1 II 1 •• w · t l f nm l m '\" ry 'L ntin nt .· · ·1 .\u ralia. I ·m~ in f th ·c tru nati\· \ h )fS · ktY b · ·n foun 1 1 uri cl in f thi ~lg in~ 11 I art· f th Cnit cl 'tat·· in .\h ka, in 1 in I~cu~ l r, I nzil an l .\ r • \. 11 ri ~ n ~Ill um . r p cl i ti n f I 9 111 ,. rt h rn ] \.. a ' i m u 1t l in th le. rg ,Yall- a . Th cliff r n tw n it ·m l th me ti H r ( fram d iagram f m cl rn hor -· :k l- 1 i.· hi fly in pr p rti n , th kull h rt r, ith cl 1 r jrnv·, ·h leg.~ rath r hnrt and f ct mall in prop rti n t th 1 cl> . I 1 h · hara t r thi f il hor r mbl an \ rgr wn z ra r· th r the. n a l m ti h r . "\\~ kn ,\ n thing f it 1 ring. It mnY haY l n trip 1, and in thi ca· w ul l haY · l n r_ · z l ra-lik ; ut th r ar om rca on f r b li ving h wa n t r min ntly trip 1 h b n , r trifi l, n h a,·y, th animal matt r f th b n haY·ing ntir l_ y l ha,·in n partl1 r plac 1 1 > min ral m·1 t r. r no mu h chc. in c 1 r h w v r an - ha th k alm t 1i 1 n . f th nati, 1 · 1 ha m · n p trifie 1 m · l n l u ri e l f r 1n--t11) th . . . . ly ·I , h m f r h. a f f 8 EVOLUTION OF THE HORSE locality is on the io brara river in ebraska, another in central Oregon. Iany separate teeth and bones have been found in the phosphate mines near Charlestown, S. C. ; other specimens have come from central Florida, from southern Texas, Arizona, Kan sas, Louisiana and even from Alaska. They are, in fact, so often found in deposits of rivers and lakes of the latest geological epoch (the Pleistocene) that the formation in the western United States has received the name of Equus Beds. In South America, in strata of the Pleistocene Epoch, there occurs, besides several extinct species of the genus Equus, the Hippidium, a peculiar kind of Horse characterized by very short legs and feet, and some peculiarities about the muzzle and the grinding teeth. The legs were hardly as long as those of a cow, while the head was as large as that of a racehorse or other small breed of the Domestic Horse. All these horses became extinct, both in orth and South America. "\ hy, we do not know. It may have been that they were unable to stand the cold of the winters, probably longer continued and much more severe during the Ice Age than now. It is very probable that man - the early tribes of prehistoric hunters - played a large part in extinguishing the race. The competition with the bison and the antelope, which had recently migrated to America - may have made it more difficult than formerly for the American Horse to get a living. Or, finally, some unknown disease or prolonged season of drought may have exterminated the race. "\Vhatever the cause, the Horse had dis appeared from the New World when the white man invaded it (unless a few individuals still lingered on the remote plains of South America), and in his place the bison had come and spread over the prairies of the orth. In Central Asia, two wild races persist to the present day; others were domesticated by man in the earliest times, and their use in Chaldcea and Egypt for draught and riding is depicted in the ancient mural paintings. In frica the larger species became extinct in prehistoric times, as in America, but the smaller zebras still survive in the southern part of the continent (one species, the Quagga, abundant fifty years ago, is now probably extinct), and the frican Wild Ass is found in the fauna of the northern THE EVOLUTION OF THE HORSE. Fonnations in Western United State.s and Characteristic Type of Horse in Each fore Fool Hind foot ll'~lh QLi3termC) Rect>nt 0 One T llt' Tc ~~e of Man I Ple1stocen Equus Srl,nt.~ of ~r' ,nl ...i 11nd 411' Ji~it, ~-:JonJ •ltl-J i~,IJ Plioctnc Three Toe Thr~c T Ol'-' Protohippus .5,de loi:'5 MJOcene nol louch1n~ lht' trounJ not louc1' inf I Terliary Th ree Toes r ~Hit tO('j Oli~ocene Mesohippus touching thr ~round; A~e of $rlint of 5~Jiiil l"hl"l'C I UC.( ",Jr ff•l'~ 1 1 5hor1· Mammal~ I 1==- , - ,- ·- ~, :::::-"§1:::::--2~=! loudHnj lht {f\"lUnd Crowntd four Toes "ifhout Protorohippus t'.ffltsnt Eocene four Toes ThH'l' TOl'S Hyrncotheriu m Splini-c;i· 1!! J1til ~,,1 ,nt 1.-I 5~J 1~it. (Eohippu.~ Hypot'1eli col Ance-'fOJ"j wi th fin•, T0t.1 on Ench f oot A~e of J urassic ond Ttelh lik~, 1htt~t. of Moo kt)'-' ti Reptil Triassi EVOLUTION OF THE HOR E l I I~ rt. Th \Yild H )rs f pr hi ·tori' burn1 ' :t small rac ·h )rt-1 ~1 g land sh:q...,gy-llair d, was l >111 •· i ·at ·cl l>) man, a fa· 1: t i h1 )\\ n fr m the rud drawing· · -raL 'h d m hrn1 or i ,r lym n )fth •· lithi' rl li·h tl ~Un .. \g\. I ulth 1 1 C>111'S- i' II r n \\. in us i · l riY l ·hi fly fr )111 th .. \sia i · ra ·' al- th 1rrh it i 1 r)l al 1 hat in th r\ i· a ·onsid ·rah]' · r .. in f thi · 'hagl·y ·h rt-1 bg d hur I an ra · an l i is]><>' ·il lt al that ... \fri an rn nn hay 1 n l m ·ii at THE EY L ''TI j, T F Tll E II R E. Th hi t n" f th Y lu i n f h Ile r thr u h th T r tiary 1 ri 1 r · mal aff r 1 th t kn "n illu:tra- ti n in rm f v luti n 1 m ·an· )f natural 1 ti n an th a la1 ta i n f a ra f animal i it n, 1ron- m 1t. Th an try f thi family ha 1 n ira cl 1 a ·kt· n arly th 1 a-inning f th T rtiary , ith ut a ingl im1 rt'tnt 1 r ak. I · thi 1 n · d f ti timat 1 'tt n 'trl) thr f " a.r. imal hr ugh im1 rtan lnnge in 'tll part f tl , bu iall __ in h t h an l fe t, a la1 tina th m m r and more I tly t ih ir 1 arti 'ular n,·ir nm nt nam 1 .. th p n plain 't hc,r at 1 lat ·au r buiun , ·i h h ir · ant., un d h rl a , "hi 'h is th' na ural hal i a f h · II r.· . In th · fan ( f h I-I )f • w '111 ra · ' ,. ry p · n f thO' mark l 1 · ·uliariti f · · · h th ' m d ·n1 II r ' frc >111 an an · st >r ,, hi h r: ha wh n i s r main , fc, md h 'tnimal wa nam d h /(Tl Jilt'rillJll () , II t tk . ifi n h 12 EVOLUTION OF THE HORSE modern quadrupeds have diverged from a single type, each be coming adapted to the needs of its especial mode of life. The earliest known ancestors of the Horse were small animals not larger than the domestic cat, with four complete toes on each forefoot and three on each hindfoot. There is reason to believe that the still more ancient ancestors of this and all other mam mals had five toes on each foot. In the forefoot of the earliest known stage we find a splint-bone or small, slender rudiment rep resenting the missing first digit or thumb, which no longer ap pears on the surface of the foot, while in the hindfoot there is a similar rudiment representing the outer or fifth digit, but no trace is left of the innermost or first digit. The proportions of the skull, the short neck and arched back and the limbs of moder ate length, were very little horse-like; recalling, on the contrary, some modern carnivorous animals, especially the civets (Viver rid 1 These numbers refer to the stages in the direct line of descent of the m odem Horse; see frontispiece. OLIGO C 0 ligoc,ene Hors es h~- . The Sid e To CE NE ._o cr ne e Four Toes in the Fore Foot, h· cc Toes 1n the Hin d Foot. RETA C IC . EO H:IPPUS UNDISCOVER ED A1NC ESTOR PROTO ROH I PPUS EPIHIPPUS MESOHIPPUS OCE N TAC EO u OCCN IDDU: OUCiOCCNC EARLY STAOES IN T HE EVOLUTION OF T HE FEET Fm111 tl11: serit~S 1_111 cxliil,iti,_, 11 in the ,\ 111cri cn 11 l\ l 11st~11111 EVOLUTION OF THE HOR E ~ 1 ht..·, ~ r jn ·t hL ~inning to sl uw signs >f tu ing int() l re 1. ·- 1 h Ir m )br t ·th baY t nly nn main ·usp, ·.p · p th ~nl urtl 1rrnlbrs n·.·tth rnubrs in ·a·l j:l\\ 1 \\}i·h t\\ ' tn l thr , r sp cti, 1:,. '1 h ml:, sp · ·im 1 s \\ hi ·h 1 ~ ·t: n f nn l w re in th L n l n l't \ )f Lo\\ ·r Lo · ·n · c f I 1~-J n l ·m l a r 1 r · · rY tl in h I ri ti · h ~ 1u: um. 'l h I ti1 i u.. is mu · h tt r h1 ), Yn. I · m · fr m th Lo\\" r L 'Il f \Yy min an l .. T \Y :\1 .·1 ·<, '1111 i· ,. r like th· fly- II FIG. 1.-UPPER AND LOWER TEETH OF EOH IPPUS," FROM THE LOWER EOCENE OF WYOMING. NATURAL SIZE • 1 otlz rlllJJl X I tha th m lar t th hay th u ITI< r 1 rly fu ing int r nd th la t 1 rm lar i b gin- .. t 1 k lik m lar·. Th t f thi ha~ f U1 nd th plint f a fifth. 'I h hi t h~ th an 1 h I lint f a11 ill f m · r h n l I h · 1 h f 16 EVOLUTION OF THE HORSE River Badlands of Wyoming, and was described by Professor Cope and others under the name of the" Four-Toed Horse." Of Orohippus we have only parts of jaws and teeth. A specimen of the forefoot is exhibited in the Museum of Yale University. s. Epihippus. UPPER EocENE. Of this stage of the evolu tion of the Horse only incomplete specimens have been found. The molar teeth have the once round cusps almost completely converted into crescents and crests, while another tooth of the premolar series bas become like the molars. The toes are still four in the forefoot and three in the hindfoot, but the central toe in each foot is becoming much larger than the side toes, a feature which may be seen in the hindfoot shown in the series in the case. (This species happens to be somewhat smaller than those found in the Middle Eocene stage, but no doubt there were others of larger size living at the same time.) Palceotherium and Paloplotherium of the Upper Eocene of Europe form a side branch of the Horse line. They were very abundant in Europe, but have not been found in the New World. On each foot they had three toes of nearly equal size, and the teeth show a rather peculiar pattern. One of these animals was thought by Professor Huxley to be a direct ancestor of the Horse, but it now is considered to be merely a collateral relative. Some species of Palceotherium were of large size, equal to a tapir. They were first described in the year r 804 by the celebrated Baron Cuvier from remains found in the gypsum quarries of Mont martre, Paris. A large series of skulls, jaws, foot-bones etc., from the Upper Eocene of France, is exhibited in one of the counter-cases. 6 and 7. Mesohippus. OLIGOCENE (White River Formation). In this stage there are three toes on each foot, a splint represent ing the fifth digit of the forefoot .of the Eocene ancestors. The middle toe is now much larger them the side toes, which bear very little of the weight of the animal. Three of the premolars ha·ve now become entirely like the molar teeth, the crests on the crown are completely formed, and the outside crest in the upper molars has taken the shape of two crescents. In the Middle Oli gocene is found M esohippus bairdi about the size of a coyote, EVOLUTIO OF THE HOR ·lil i1 h 1)1 · l''ltr \It· ,1,·ppu, ,'nt ·111 li1t a 1 h l· tnim t1 all I a ·t. f tl • 11 . l II FIG. 2.-UPPER A D LOWER TEETH OF MESOHIPPUS BAIRD I, " FRO T H E IDDLE OLIGOCE E OF SOUTH DAKOTA. NATURAL SIZE _·hi . in th u 1t r-ca b i e the p c1men h wn in the f f t n l in h ne of kull . Anchitherium. L \YER l\fiocE. TE . Thi tacr ha· 1 n i 1 Eur p n l in .\ merica. It i mu h like it· pr d ·- 1 l ha th re t f th t th , >Ill '\\ ha e. It pr 1 ably i. n t in the lire line f . t i n a icle branch. .\ 1 ala r w , c ... hibit · d her . Parahi pus , 1 l Hypohippus . . f IDDLE .fr 'E~ E. In/ ir- o · c r much · '"' er ·m 1 I 11 • 1 h- l . 20 EVOLUTION OF THE HORSE H ypohippus small rudiments still remain representing the first and fifth digits, but there is no splint of the fifth, as in M esohippus. The second and fourth digits still touch the ground, though lightly. A metacone, ---paracone metaconule-- D 1 1 I protoloJJh FIG. 3.-UPPER MOLAR OF MODERN HORSE, SHOWING EARLY STAGES OF WEAR OF THE TOOTH. CROWN VIEW. NATURAL S'ZE The feet of Parahippus were much like those of Hypohippus, but the side toes were smaller. 10 and 1 I. Protohippus and Pliohippus. MIDDLE and 0 COO 00 E OLUTIO OF THE HOR E 2 I 1 this h T \\ 1 s l I ti ' ll] l · 111 u ·h ·. > I 11 ,h 1 pp r 111 t . , ·ith "ith11 ti h \' .. 11 \' 11 l \ 1 . !Ill t, .-l th .. t with h w ai · .l l l k l in ·i l 1 · t l n tin a · 1 I 1 t 1i.· , ~ .... the -urfa e f th t th ha a · >f nam l · d - - · r 1· 'tino- a littl' a ,-e th 0 rin liner urfa u. the - :---. .'.:") ·, 1 • • r m t rial n a h -ide w ar- l wn in h 11 w ·, > t n Y r kn:--. ff. c .. u h y ~ r ra' 1 th r u~7 hl) n ea ·h i 1 ' . .· ~ \' r_ nt in trum nt f r orin liner har 1 ?"nt · c ·. In z'pp ,- , n l Plz'olzippu , · 11) in th f rm r th · h ·h ar y n m a n a in the m l ~rn l ; · h y mu t th ·· , · ar \Yly r '"' ar ut at an arlicr Th f t in h e t,Yo g nera ha,.. but one t e tou hiner the 1cl. Th id t ( c nd and fourth cli 0 it ) ar c m1 let u h m 1 nd r than in the earlier tao an are a1 - ly u , a · th * • cannot reach the r und. In ome f Pliolzippus th y haYe alma t di app ar l. The f r - · Protolzippus till r tain tiny n ul f b ne at th l .. ·k · h ·· Ti t ( ometim improperly call in the Hor·· th · k 1 -j i 1t 'J which ar the r main of the fir t an l fifth ligi . Hipparion. Pu E. ·E. Thi. 0 enu pr a 1) al i 1 h f . 1 tr f th h r c famih i mu ·h 1ik P ot hi n ,Yith m mplicati n al h n in th ~ur p an I Ii l h al . Th . are ill th ·ot lzi 1t 24 EVOLUTION OF THE HORSE Hippidium. PLEISTOCENE. SouTH AMERICA. The feet are like those of Equus, except that they were short and stout. The teeth are like those of Pliohippus, from which it is supposed to be descended. The skull is large and long with very long slender nasal bones. Casts of the skull and limbs presented by the Museo Nacional of Buenos Ayres, Argentine Republic, are ex hibited here. MEANING OF THE CHANGE IN FEET AND TEETH. Along with the disappearance of the side toes in the evolution of the Horse there is a considerable increase in the proportionate length of the limbs, and especially of the lower part of the leg and foot. The surfaces of the joints, at first more or less of the ball and-socket kind, which allo,vs free motion of the limb in all direc tions, become keeled-and grooved like a pulley-wheel, permitting free motion forward and backward, but limiting the motion in all other directions and increasing considerably the strength of · the joint. By this means the foot is made more efficient for locomotion over a smooth regular surface, but less so for travel ing over very rough ground, and it becomes of little use for striking or grasping or the varied purposes for which the feet of polydactyl animals are used. The increased length in the lower leg and foot increases the length of the stride without decreasing its quickness. The heavy muscles of the leg are chiefly in the upper part, and to in crease the length of the lower part change~ the centre of gravity of the limb very little. Consequently the leg swings to and fro from the socket nearly as fast as before, since in an ordinary step the action of the leg is like that of a pendulum and the speed of the swing is regulated by the distance of the centre of gravity from the point of attachment, as that of a pendulum is by the height of the bob: To increase the length of lower leg and foot therefore gives the animal greater speed; but it puts an increased strain on the ankles and toe-joints, and these must be strengthened correspondingly by converting them from ball and-socket joints to "ginglymoid" or pulley joints. Additional strength, likewise at the expense of flexibility, is obtained by the consolidation of the two bones of the fore-arm (ulna and - th gr Th bl to accomm - u on mooth groun of peed. ~~"o-ny t tire of a bi · ft oad and i · g on a mooth road. le allo of mpe the animal irregular ground. of the tee h from t or long-cro d com EVOLUTION OF THE HORSE small one, in order to keep up a proper amount of activity. On the other hand a large animal is better able than a small one to defend itself against its enemies and rivals. Consequently, as long as food is abundant, the larger animals have the advan tage over their smaller brethren, and by the laws of natural se lection the race tends to become continually larger until a limit is reached, when sufficient food becomes difficult to obtain, the RESTORATION OF THE FOUR-TOED HORSE Oldest known Ancestor of the Modern Horse; only r 6 inches high Photo from original watercolor by C. R. Knight, based on mounted skeleton in American Muse um animal b~ing compelled to devote nearly all its time to getting enough to eat. CAUSE OF THE EVOLUTION. The evolution of the Horse, adapting it to live on the dry plains, probably went hand in hand with the evolution of the plains themselves. At the commencement of the Age of Mam- EVOLUTION OF THE HOR E ·, n~tl · th \\" · l 1"11 p · 1 rt of l h . · ort h . \ 111 ·ri ·an ·rnlt in ·n ,, a s l \ 1 m llb ~ts hig-h ~th \" s ·~1-l ,. ,1 as tl<>\\'. ( ~r ·a parts of i had l ut r · ntl~· m 'rg l an l th ruH of ~l ·i '<) sti11 s r ·t ·h ·cl fa r 11 h all :· f th ~lissi. sip] i. '1 h ·hmat al llw 1111 • , a s l rl l al h"' Y ·ry nH ist, warm and trn1 i ·al, as is shm, n 1>\ th· r l i ·:d f r :t tr s, f )lllHl ft ssil ,. n a· far as rr' nland. 'u ·h ·limat . with th h w 1 ,·a il,n )[ th land woul 1 ~r wth f c..l n ft r t ~ all ,. r th ounlr_ , ancl o su ·h ·oncli ti n · f lif th animal · t f th 1 ginning < f h' mammalian I ri l mu~t haY 1 n a lapt ll. I uring h' 1 )r iar , h' · m tin nt \Ya ~ t adily· ri ing a ,- , h) , an-1 '\r ·l 'l11d 'l h :am · tirn th r influ n . w r at w rk t rnak th ·limat continu- ~ lh· l l r an l lri r. Th mina n f 11 lr · ri t cl ~ n l thinn an 1 a h c I p aran · ancl .·t n ·i n f p n, ra · Th an i nt f r t inhal itants \\ · l ith r t r li c I pear with th f , r t ) 11 h· t th n w nditi n f lif . Th · an ·tors < f th H r · \ f 11 wino- th latt r cl with th chancring n Iii n~. an 1th ra fincll a~ we i to- la),< n of -h mn:t highly p cializ cl animal· in it ach1 tation t< j s uliar n,·ir nm nt. .. \ t h nd f h .. \ a f ~Iammal · th · ntin nt.· l a a hi0 h r 1 ,·c. tion than at 1 r · nt, and th r' ., ' } r a l la n 1 nn i n b t\\ n .. \ ia a ncl ..... orth .. \ m ri ·a. as ,,. ·ll r tho.· · n \\' . ~j tin9". ..\t thi tim th Hor: 1 , ·am · lit·m. ancl inhabi l h 1 lain cf all th gr a · m 111 ·n . , ing _\u trali·t. I i , l · ''" h th r th cl i r an · ... t n · <> f h m < cl rn H r l h cl f >r in \V · ·t rn .\m ·ri ·a or in th· 1i tl · · I~a ·t ·r 1 .\. ia. I i al , unkn< ,wn \\ h · n · · h inh; l>i >r h and ,u h .\m ri -. ~rt ,,f~lansh,,11, la· n 3 \ \'il I ,f u 1 30 EVOLUTION OF THE HORSE p ARALLEL EVOLUTION IN OTHER RACES. It is interesting to observe that while the evolution of the Horse was progressing during the Tertiary period in North Arnerica another group of hoofed animals, the Litopterna, now extinct, in South America evolved a race adapted to the broad plains of Argentina and Patagonia and singularly like the Horse in many ways (see exhibit in A-case in centre of hall). These animals likewise lost the lateral toes one after another, and con centrated the step on the central toe; they also changed the form of the joint-surfaces from ball-and-socket to pulley-wheel joints; they also lengthened the limbs and the neck; and they also lengthened the teeth, and complicated their pattern. Unlike the true Horse, they did not form cement on the tooth, so that it was by no means so efficient a grinder. This group of animals native to South America became totally extinct, and were succeeded by the horses, immigrants from North America, which in their turn became extinct before the appearance of civilized man. Many of the contemporaries of the Horse in the northern hemisphere were likewise lengthening the limbs, lightening and strengthening the feet, elongating the tooth-crowns to adapt themselves to the changing conditions around them, but none paralleled the Horse Evolution quite so closely as did the pseudo horses of South America. But the camels in America, the deer, antelope, sheep and cattle in the Old World progressed on much the same lines of evolution, although their adaptation was not to just the same conditions of life. --=------' TH M RIC MU EUM JO R AL. Ent ·.·o . llo EY, Editor. F R•. ' KM. HAP. I .· , L u1s I . GRATAC AP, Adv isory Board. "W ILL I.A I K. GR EGO RY. I u d :m nthly , e. ccpt from J uly to cptember , inclusive. ubscription, One Dollar per year. For sale at t he Museum at t en cents per copy. rip i n . hould be ad ressed t o T he E dit or, American Iu scum J ournal, .Iu eum of. ·atural H istor y , 77th treet and Eighth venue. Guide Leaflets. Issued as supplements to THE A~IER IC A.. IusEu.1 J ouR AL. No. I. THE BIRD ROCK GROUP. By FRA · K 11. CHA PMA ·, Associate Curator of Ma:.1: 1alogy and Ornit hology. October, 190 1. I o. 2. THE SAGINAW VALLEY COLLECTION. By HARLA~ I. S. u TH, Assistant urator of .. rchreology. Dece~nber, 1 9 01. o. 3. THE HALL OF FOS IL VERTEBRATES. By W. D ... IATTHEW, Ph.D., istant urator of \ ertebrate Palreontology. January, 1902. o. 4. THE COLLECTION OF MINERALS. By LoUis P . GRATACAP, .M., Cura t r i · ineralooy. February, 190 2 . .. o. 5 . NORTH AMERICAN RUMINANTS. By J. A. ALLE. , Ph.D., urator of . ammalo!!y an n.~th 1 e-y. • farch, 1902. o. 6. THE A CIE T BASKET MAKERS OF SOUTHEASTE RN UTAH. y. 1EORGE H. PEPPER, Assistant in the D partm n t f An ·h r p lo y . . pril, 1 90 _ o. 7. THE BUTTERFLIE OF THE VICI ITY OF NEW YORK CITY. By ·11.LIA t BE ' TE • •. t .. LLER, urator of Entom l o. 8. THE o. 9. IL LU u.l ., . r r, J O • American Museum of Natural History. WHAT IT IS DOING FOR THE PUBLIC: Gives free admission to its halls on Wednesdays, Thursdays, Fridays, Saturdays and Sundays. Provides for free illustrated lectures on Tuesdays and Saturdays. Provides for free illustrated lectures to teachers on Saturdays. Provides instruction to school children when accompanied by teachers. WHAT IT IS DOING FOR ITS MEMBERS: Gives free admission at all times. Provides special courses of illustrated lectures. Gives free use of Library. Issues the Journal. Distributes Guide Leaflets. WHAT IT IS DOING FOR SCIENCE: During the year 1902 it maintained exploring parties in various parts of the United States and in: Siberia, Alaska, Central America, Greenland, China, British Columbia, Venezuela, Baffin's Bay, Japan, Mexico, Martinique, Hudson Bay, The Bahamas, St. Vincent, Cuba. Maintains scientific publications: Memoirs-twenty-two have been issued. Bulletins-sixteen volumes have been issued. Journal-two volumes have been issued. What the Museum Needs. Additional members. Increased subscriptions to defray expenses of exploring expeditions. Funds to make additional groups similar to those in the Bird, Mammal, and Ethnology Halls. Small sums sufficient to preserve the records of the Indians of New York. Means for collecting and preserving representative examples of animals on the verge of extinction. Means for collecting fossils and geological specimens. Membership Fees : Annual Members, ...... $ 10. Life Members, ...... 100. Fellows, ...... 500. Patrons, ...... 1 ,ooo. All money received from membership fees is used for increasing the collections. Publications. The publications of the Museum consist of an Annual Report, in octavo, about 80 pages ; the Bulletin, in octavo, of which one volume, consisting of about 400 pages, and about 2 5 plates, with numerous text figures, is published annually ; the Memoirs, in quarto, published in parts at irregular intervals; an Ethnographical Album, issued in parts, and the American Museum Journal.