294. THE POPULAR SCIENCE MONTHLY. 



collection has yielded evidence of the most striking character in regard 

 to this question of the. pedigree of the horse. Indeed, the evidence 

 which Prof. Marsh has collected tends to show that you have in Amer- 

 ica the true original seat of the equine type the country in which the 

 evidence of the primitive form and successive modifications of the horse 

 series is far better preserved than in Europe ; and Prof. Marsh's kindness 

 has enabled me to put before you the following diagram, every figure in 

 which is an actual representation of the specimen which is preserved in 

 New Haven at this present time. The succession of forms which he has 

 brought together shows, in the first place, the great care and patience 

 to which I have referred. Secondly, there is this Pliocene form of the 

 horse (Pliohippus) ; the conformation of its limbs presents some very 

 slight deviations from the ordinary horse, and with shorter crown of 

 the grinding teeth. Then comes the form which represents the Euro- 

 pean JTipparion, which is the JProtohippus, having three toes and the 

 forearm and leg and teeth to which I have referred, and which is more 

 valuable than the European Hipparion for this reason : it is devoid 

 of some of the peculiarities of that form peculiarities which tend to 

 show that the European Hipparion is rather a side branch than one 

 in the direct line of succession. Next comes the Jfiohippus, which 

 corresponds pretty nearly with what I spoke of as the Anchitherium 

 of Europe, but which lias some interesting peculiarities. It presents 

 three toes one large median and two lateral ones ; of the toe which 

 answers to the little finger of the human hand, there is only a rudi- 

 ment. This is, however, as far as European deposits have been ena- 

 bled to carry us with any degree of certainty in the history of the 

 horse. In the American tertiaries, on the contrary, the series of 

 equine forms is continued down to the bottom of the Eocene. The 

 older Miocene form, termed Mesohippus, has three toes in front and 

 a large splint-like rudiment representing the little finger, and three 

 toes behind. The radius and ulna are entire, and the tibia and fibula 

 distinct, and the teeth are anchitheroid with short crowns. 



But the most important discovery of all is the Orohippus 

 which comes from the lower part of the Eocene formation, and is 

 the oldest member of the equine series known. Here we have four 

 complete toes on the front-limb, three toes on the hind-limb, a well- 

 developed ulna, a well-developed fibula, and the teeth of simple pat- 

 tern. So you are able, thanks to these great researches, to show that, 

 so far as present knowledge extends, the history of the horse-type is 

 exactly and precisely that which could have been predicted from a 

 knowledge of the principles of evolution. And the knowledge we 

 now possess justifies us completely in the anticipation that when the 

 still lower Eocene' deposits and those which belong to the Cretaceous 

 epoch have yielded up their remains of equine animals, we shall find 

 first an equine creature with four complete toes and a rudiment of the 

 innermost toe in front, and probably a rudiment of the fifth toe in the 



