FOSSIL MAMMALIA. 



55 



Meanwhile, we cannot but recognise, in the anchylosed and confluent state of the 

 bones of the fore-arm and leg, a marked tendency in it towards the Ruminant 

 Order, and the singular modifications of the cervical vertebrae have enabled us to 

 point out the precise family of that order, with which the Macrauchenia is more 

 immediately allied. 



In first demonstrating this relationship, it was shown in how many particulars 

 the CameUdce, without losing the essential characters of Ruminantia, manifested 

 a tendency to the Pachydermatous type ; and the evidence which the lost genera, 

 Macrauchenia and Anoplotherium, bear to a reciprocal transition from the Pachy- 

 derms to the Ruminants, through the CameUdce, cannot but be viewed with 

 extreme interest by the Zoologist engaged in the study of the natural affinities of 

 the Animal Kingdom. 



The Macrauchenia is not less valuable to the Geologist, in reference to the 

 geographical distribution of animal forms. It is well known how unlooked-for 

 and unlikely was the announcement of the existence of an extinct quadruped 

 entombed in the Paris Basin, whose closest affinities were to a genus, (Tapirus,) 

 at that time, regarded as exclusively South American. Still greater surprise was 

 excited when a species of the genus Didelphys was discovered to have co-existed 

 in Europe with the Palceotherium. 



Now, on the other hand, we find in South America, besides the Tapir, which 

 is closely allied to the Palaaothere, — and the Llama, to which the Anoplothere 

 offers many traces of affinity, — the remains of an extinct Pachyderm, nearly 

 akin to the European genus Palceotherium : and, lastly, this Macrauchenia is 

 itself in a remarkable degree a transitional form, and manifests characters which 

 connect it both with the Tapir and the Llama. 



ADMEASUREMENTS OP THE BONES OF THE MACRAUCHENIA. 



Length of third (?) cervical vertebra 

 Vertical diameter of ditto 



Do. do. of body of ditto 

 Transverse diameter of ditto 

 Vertical diameter of spinal canal 

 Length of fourth lumbar vertebra 

 Vertical diameter of body of ditto 

 Transverse diameter of ditto 

 Vertical diameter of spinal canal 

 Transverse ditto ditto * 



Inches. 



Lines 



7 



9 



4 







2 



3 



3 



3 



1 





5 



5 



2 



9 



2 



10 



1 



1 



1 



c 



* This diameter increases rapidly in the posterior lumbar vertebras, in correspondence with the enlarge- 

 ment of the spinal chord, which gives off the great nerves of the hinder extremities. 



