313 



author in the Appendix to the ' Natural History of the Voyage of 

 H.M.S. Beagle.' 



The subsequent acquisition by the British Museum of the collec- 

 tion of Fossil Mammalia brought from Buenos Ayres by M. Bravard, 

 has given further evidence of the generic distinction of the Sceli- 

 dothere, and has supplied important characters of the osseous system, 

 and especially of the skull, which the fragments from the hard con- 

 solidated gravel of Punta Alta did not afford. 



The best portion of the cranium from that locality wanted the facial 

 part anterior to the orbit, and the greater part of the upper walls ; 

 sufficient however remained to indicate the peculiar character of its 

 slender proportions, and hence Professor Owen has been led to 

 select the name leptocephalum for the species, which is undoubtedly 

 new. 



The aptness of the epithet 'slender-headed' is proved by the author's 

 researches to be greater than could have been surmised from the 

 original fossil ; for the entire skull, now in the British Museum, 

 exhibits a curious and very peculiar prolongation of the upper and 

 lower jaws, and a slenderness of the parts produced anterior to the 

 dental series, unique in the leaf-eating section of the order Bruta, and 

 offering a very interesting approximation to the peculiar proportions 

 of the skull in the Ant-eaters. 



The original fossils from Patagonia indicated that they belonged to 

 an individual of immature age : the difference of size between them 

 and the corresponding parts in the British Museum, depends on the 

 latter having belonged to full-grown individuals : the slight difference 

 in the shape of the anterior molars seems in like manner to be due 

 to such an amount of change as might take place in the progress of 

 growth of a tooth with a constantly renewable pulp. Professor Owen 

 finds at least no good grounds for inferring a specific distinction be- 

 tween the mature if not old Scelidothere from Buenos Ayres, and the 

 younger specimen from Patagonia. 



The author then proceeds to give a detailed anatomical account of 

 the fossil bones in the British Museum, instituting a comparison 

 between them and the bones of other large extinct animals, especially 

 those of the Edentate order. 



The Scelidothere was a quadruped of from 8 to 10 feet in length, 

 but not more than 4 feet high, and nearly as broad at the haunches ; 



