REVIEWS. 309 
Of icti m exclusive of n» Je pe — of seven species of six genera 
belong to the Dakota miocene, h erium and us are mon 
to the European te “tt tiary, The remaining genera in an but imperfectly known, appear to be 
pes ES - Niobrara pliocene presents us with traces of a peccary, but rahe ‘probably may 
neriod 
e of the artiodaety le genera of the Dakota miocene, the huge pasion: was repre- 
ienn by the nearly allied Chalicotherium of the European and Himmalaya miocene period, 
Of uneven-toed Pachyderms or Perissodactyla, the Dakota egre presents one Acera- 
therium, a peeuliar genus of the same family, the Hyracodon, and a species of Lophiodon. 
The former and latter are both European tertiary forms. Another member of the Rhinoceros 
family, R. hesperius, from California, was probably an Aceratherium of miocene age. A. merid- 
ianus of Texas was probably of the sume CART as the latter. 
The Niobrara plioeene p m tl Rhinoceros, odon and Elephant. 
The for A gh ab aiaa t in its Europear 
equiva alen ai and continuing to exist in Asia and Africa, nh qct E ed to the sub- 
genus Tetralophodon, wine that ea me qM period was a Trilophodon. Elephants of 
other species were nearly y e but two Fiunt now live 
in Asia and Africa. 
Five genera of So lipeds appear to have lived in North America during the miocene period. 
Three of them are peculiar, and appear st to have been discovered elsew ere They have 
been named Anchippus from Texas, Hypohippus from the Niobrara Rive pappaa 
from New Jersey. The remaining genus ppsa characterized sg ud Pe of 
maius from the Mauvaises Terres belongs also to the European miocene. 
he Niobr: 
The pliocene formatio: Niobrara is remarkable for the abundance of its equine 
mains, which have been referre e genera, of which Merychippus and Parahippus ae 
pecu bu r, and Protobippus has been discovered cleewhe ag - ly in a America. The re- 
American quaternary and like- 
" 
The miocene “Rodents of the. Án Terres belong to four peculiar genera of as many 
still existing families. D genera, Palzocastor, may be identical with the European 
ene f Cotemporan 
The pliocene Rodents e a Me pa appear to belong to the still existing g Castor 
and irri, but the latter now exists only in the old wor! 
Of t w discovered qua ternary rodents o f North America, one genus, Hydrocherus, now 
S RR 
The miocene Insectivora of North America belong to three genera no discovered else- 
where." pp. 359-362. 
viewing the character of the work, the care and accuracy of t 
spect constitutes its great merit. On the other hand, however, we d to 
in many cases, that exact comparison and clear diagnosis of era 
proposed or adopted, by which the zoological affinity is alone RE 
and by means of which the analysis of the subject in the broad sense is 
so greatly facilitated. Without it, the student gropes in a mass of detail, 
'and unless he fortunately have access to a good museum, will fail of 
acquiring a mastery of it. This refers also to a precise comparison with 
Eur DEYS nem for which we have so many standards in figures and 
The EEN of extinct mammalia is of equal or greater value to the 
student. The whole number of species enumerated is two hundred and . 
three, of which Dr. Leidy has stood sponsor to one viget and twenty. 
'The speen are distributed into the orders as follow ; Cédivbes, thirty- 
three iodactyla, fifty-two; Perissodactyla, hcec Rodentia, 
iwastr! Insectivora, five; Marsupialia, one; Edentata, seven; Sirenia, 
