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, Macrauchenia and Myrmecophaga). 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. 1 

 The placenta is diffuse, as in the Suina and Tragulina, not coty- 

 ledonary, as in the Pecora. Finally, the Camelidce 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. 



Camelusr — Dentition of adult : i ^, c ^, p %, m % ; total 34. First 

 upper premolar simple, placed immediately behind the premaxilla?, 

 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 premaxillte not articulating 

 with the arched and somewhat elongated nasals. Vertebra? : C 7, 

 I) 12, L 7, S 4, 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. hactrianus, Fig. 114). 3 The former 



1 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. 



2 Linn. Syst. Nat. 12th ed. vol. i. p. 90 (1766). 



3 There is much confusion as to the proper use of the names Camel and 

 Dromedary. It is now generally accepted that the former is the 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 



