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VI. On the Molar Teeth , Lower Jaw, of Macrauchenia patachonica, Ow. 
By Professor Owen, F.B.S. 
Received April 21, — Read June 10, 1869. 
The dentition of a Mammal so rare and interesting as the Macrauchenia deserves better 
illustrations than the single reduced view of the lower molars given in 1 845 * * * § , and the 
still more reduced figures of both upper and lower teeth lithographed by BRAVARDf . 
The intention to communicate to the Royal Society a description with figures of the 
natural size of the specimen of mandible and teeth, still unique, in the British Museum, 
has been deferred in the hope of acquiring from South America other fossil remains, 
especially the upper jaw and teeth of Macrauchenia patachonica ; but such fossils have 
not yet come under my observation. The recently obtained knowledge, however, of the 
former existence of another large quadruped in America, with cameline characteristics 
of the cervical vertebrae like those in Macrauchenia , coupled with true cameline affinities, 
as exemplified by the dentition of the lower jaw in Palauchenia , induces me no longer 
to delay the adequate record of the characters which so strikingly distinguish the perisso- 
dactyle from the artiodactyle forms of hoofed quadrupeds with the intraneural course of 
the vertebral arteries in the region of the neck. 
The specimen here described formed part of a series of fossils from Buenos Ayres, 
purchased for the British Museum in 1845. I was requested by Mr. Konig, the then 
Keeper of the Department of Mineralogy, to examine and report on that Collection, 
which chiefly consisted of Megatherian remains^, and I was led by the conclusions 
which I had formed of the pachydermal affinities of the genus Macrauchenia , based on 
bones of the trunk and limbs described in the ‘Fossil Mammalia of the Voyage of the 
Beagle ’§, to recognize the mandibular specimen with teeth as belonging to that genus, 
and I accordingly figured it as such in the concluding part of my ‘ Odontography.’ 
The specimen (Plate VIII. figs. 1-3) consists of the part of the left ramus of the lower 
jaw of a full-grown individual, with six consecutive grinders, anterior to which the jaw 
is broken away, as is also the hind end of the ramus about 3 or 4 inches behind the 
last grinder. The first tooth in place answers to the second premolar (Plate. VIII. figs. 
1-3, p 2) of the typical series. It is implanted by two fangs, supporting a lamelliform 
* Owen’s ‘ Odontography,’ pi. 135. fig. 7, p. 602. 
t Published by Burmeister, in the ‘ Anales del Museo Publico de Buenos Aires,’ Entrega Primera, 4to, 1864, 
pi. 1. 
+ See Owen’s ‘ Memoir on the Megatherium,’ 4to, 1860, p. 11. 
§ 4to, 1840, pp. 35-56, pis. vi.-xv. 
