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ribs, 7. e. pleurapophyses ; but these become broad and remain short, 
and coalesce with the centrums and diapophyses of their respective 
vertebre ; and the anthropotomist then calls them ‘ transverse pro- 
cesses, and distinguishes them as being perforated, the foramen 
being the space included between the centrum, the diapophysis, and 
the pleurapophysis. 
Another remark is suggested by the skeleton of the Aurochs, 
touching the true value of the character of its fourteenth pair of free 
pleurapophyses. In the genus Bos proper there are only thirteen 
pairs. In the American Bison there are fifteen pairs. According to 
the artificial character in anatomy of the ‘ dorsal vertebrz,’ the above- 
cited Bovide have been supposed to differ actually in the number of 
their vertebrz, whereas this is absolutely the same in each of them; 
after the seven cervical vertebre there are nineteen true vertebre, 
z. e. nineteen vertebre between the iast cervical and the sacral ver- 
tebre. Inthe embryos of many Ungulates, rudiments of ribs (pleur- 
apophyses) are found moveably attached to vertebr, to which they 
afterwards become anchylosed, and accordingly are called lumbar 
vertebre. In the Aurochs these elements retain their freedom and 
growth in one more vertebra than in the common Ox; in the Bison 
two more vertebrz have moveable pleurapophyses. Accordingly we 
find that if the common Ox has but thirteen dorsal vertebre, it has 
six lumbar vertebre; if the Aurochs has fourteen dorsal, it has five 
lumbar ; and if the Bison has fifteen dorsal vertebre, it has but four 
lumbar. But the unity of the numerical character of the true ver- 
tebrz does not stop here; for when we find, e. g. in the Dromedary, 
the Camel, the Llama, and the Vicugna, only twelve dorsal vertebre, 
the typical nineteen is completed by seven lumbar vertebre ; and 
this number is never surpassed in the Ruminants. Most of the species 
agree with the common Ox in the number of the true vertebre that 
retain their pleurapophyses in moveable connection. The Reindeer 
and the Giraffe resemble the Aurochs in having fourteen dorsal ver- 
tebre. But what perhaps is still more interesting and usefully in- 
structive as to the true affinities of the hoofed quadrupeds with toes 
in even number, is the fact, that besides their common possession of 
a complex stomach and simple cecum, of a peculiar form of astra- 
galus, of a femur with two trochanters, and of a symmetrical pattern 
of the grinding surface of the molar teeth, they also agree, as I have 
shown in my paper on the genus Hyopotamus, in having nineteen 
natural segments of the skeleton, neither more nor less, between the 
neck and the pelvis. The Babiroussa, the African Wart-hogs (Pha- 
cocherus), and the extinct Anoplotherium, resemble the majority of 
Ruminants in having thirteen dorsals and six lumbars ; the Wild Boar 
and the Peccari resemble the Aurochs in having fourteen dorsals and 
five lumbars ; the Hippopotamus resembles the Bison in having fifteen 
dorsals and four lumbars. 
This constancy in the number of the true vertebre in the Artio- 
dactyle Ungulates is the more remarkable, and demonstrative of their 
natural co-affinity, by contrast with the variable number of those 
vertebre in the odd-toed or Perissodactyle group, in which we find 
