296 UNGULATA 
the transmission of the vertebral artery, which does not perforate 
the transverse process, but passes obliquely through the anterior 
part of the pedicle of the arch (a condition only found in two other 
genera of mammals, J/ucrauchenia and Ayrmecophaya). There are 
no horns or antlers. Though these animals ruminate, the stomach 
differs considerably in the details of its construction from that of 
the Pecora. The interior of the rumen or paunch has no villi on 
its surface, and there is no distinct psalterium or maniplies. Both 
the first and second compartments are remarkable for the presence 
of a number of pouches or cells in their walls, with muscular septa, 
and a sphincter-like arrangement of their orifices, by which they can 
be shut off from the rest of the cavity, and into which the fluid 
portion only of the contents of the stomach is allowed to enter.! 
The placenta is diffuse, as in the Suina and Tragulina, not. coty- 
ledonary, as in the Pecora. Finally, the Camelide differ not only 
from other Ungulates, but from all other mammals, in the fact 
that the red corpuscles of the blood, instead of being circular in 
outline, are oval, as in the inferior vertebrated classes. 
Camelus.2—Dentition of adult : 74, ¢4, p 3, m3; total 34. First 
upper premolar simple, placed immediately behind the premaxille, 
and separated by a long diastema from the penultimate tooth of 
that series. Lower incisors somewhat proclivous, the outermost the 
largest. Skull elongated, with an overhanging occiput, orbits com- 
pletely surrounded by bone, and the premaxille not articulating 
with the arched and somewhat elongated nasals. Vertebre: C 7, 
D 12, L 7, 84, C 13-15. Ears comparatively short and rounded. 
One or two dorsal adipose humps. Feet broad, with the toes very 
imperfectly separated. Tail well developed, tufted at the end. 
Hair nearly straight, and not woolly. Size very large and bulky. 
The genus is now represented by two species, viz. the single- 
humped Arabian Camel (Camelus dromedarius), and the double- 
humped Bactrian Camel (C. bactriunus, Fig. 114).3 The former 
* The stomach of the Camel inhabiting the Arabian desert is commonly 
looked upon as a striking example of specialised structure, adapted or modified 
in direct accordance with a highly specialised mode of life ; it is therefore very 
remarkable to find an organ exactly similar, except in some unessential details, 
in the Llamas of the Peruvian Andes and the Guanacos of the Pampas. No 
hypothesis except that of a common origin will satisfactorily account for this, 
and, granting that this view is correct, it becomes extremely interesting to 
find for how long a time two genera may be isolated and yet retain such close 
similarities in parts which in other groups appear readily subject to adaptive 
modifications. 
> Linn. Syst. Nat. 12th ed. vol. i. p. 90 (1766). 
® There is much confusion as to the proper use of the names Camel and 
Dromedary. It is now generally accepted that the former is tho common term 
for all the members of the genus, and that Dromedary should be confined to the 
lighter and swifter breeds of the one-humped species. One of the oldest pictures of 
