SOUTH DAKOTA SCHOOL OF MINES 75 



new world, described by Leidy; Magacerops brachycephalus 

 Osborn, a short headed animal with a great-horned appear- 

 ance, described by Osborn; Neohipparion whitneyi Gidley, 

 a new world, small horse described by Gidley and named in 

 honor of W. C. Whitney; Protoceras celer Marsh, a fleet- 

 footed first-horned animal described by Marsh; Protosorex 

 crassus Scott, a large sized primitive shrew, described by 

 Scott. 



It would lead us too far away to go into the full details 

 of this nomenclature. One additional feature, however, de- 

 serves notice in view of its not infrequent perplexity. The 

 individual who first describes a new species is supposed to 

 give it a name which must not conflict with any name used 

 previously for another species. According to the rules gov- 

 erning the matter the name by reason of its priority can not 

 be changed subsequently except for cause. Often in paleon- 

 tological work where poor or insufficient or aberrant ma- 

 terial has been first studied later discoveries have shown 

 errors of description or improper identification in which 

 case a new name may become necessary. The new name, 

 if properly given becomes the accepted name while the old 

 name is referred to as a synonymn. In not a few cases there 

 are several synonyms and not infrequently it is a matter of 

 some conjecture as to just which is the most appropriate 

 under the circumstances. 



With rare exceptions the animal life of the White 

 Kiver badlands is restricted to the Vertebrata — the back- 

 boned animals. Aside from turtles of which there are many, 

 and a few crocodiles, lizards, and birds eggs, all of the 

 fossil remains of the vertebrates thus far found within the 

 area belong to the great class "Mammalia." The term 

 "Mammalia" includes all hair-clad, vertebrated animals, 

 the females of which are provided with glands for secreting 

 milk for the early nourishment of the offspring. They are 

 the highest of the vertebrates, possessing that happy com- 

 bination of anatomical and physiological simplicity and 

 complexity tending toward highest efficiency as organisms. 

 They are not only the most important animals of today, 

 but they have been the rulers of the animal world since 

 early Tertiary time. Continuing back in geological history 

 with ever increasing simplicity toward a generalized, omni- 

 vorous, allotherian ancestry they may be traced with cer- 



