File:The Americana - a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc. of the world (1903) (14597887238).jpg

Identifier: americanauniver08beac (find matches)
Title: The Americana : a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc. of the world
Year: 1903 (1900s)
Authors: Beach, Frederick Converse, 1848-1918 Rines, George Edwin, 1860-
Subjects: Encyclopedias and dictionaries
Publisher: New York : Scientific American Compiling Dept.
Contributing Library: Robarts - University of Toronto
Digitizing Sponsor: University of Toronto

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the horse. Commencing with the Hyraeotlierium, 12stages have been recognized from as manysuccessive formations, showing the gradual evo-lution of the race into its modern form, andeach stage is characteristic of its particulargeological horizon. Some of the stages havebeen found in several parts of the world, butby far the most complete and best known seriescomes from the Tertiary Bad Lands of the West-ern States. Besides the main line of descentwhich led into the modern horses, asses andzebras, there were several collateral brancheswhich have left no descendants. Of some stagesall parts of the skeleton have been found, ofothers, only the jaws, or jaws and feet, areknown. We can mention only the more im-portant stages. I. The Hyraeotlierium is the most primitivestage known, but only the skull has been found,so that it has not been determined exactlywhat the feet were like. The teeth display sixrounded knobs or cusps on the upper molars andfour on the lower ones, and these are just be-
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HORSE pinning to show signs of fusing into cross-crests. The premolar teeth have only one maincusp, except the third and fourth premolars(next the molars) in each jaw, which have twoand three, respectively. The only specimenswhich have been found were in the London Clayor Lower ljieeiie of Kngland and are preservedin the British Museum. 2. The Eohippus is much better known. Itcomes from the Lower Eocene of Wyoming andNew Mexico, and is very like the Hyracotheriumexcept that the molar teeth have the cusps moreclearly fusing into cross-crests, and the lastpremolar is beginning to look like one of thetrue molars. The forefoot of this animal hasfour complete toes and the splint of a fifth. Thehind foot has three complete toes and the splintof another. 3. Protorohippus. In these animals thesplint of the first digit in the forefoot and thesplint of the fifth digit of the hindfoot havedisappeared, but there are still four completetoes in the fore- and three in the hindfoot. Thecrests on the

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