Royal Society. 249 



this extensive and difficult family. However, the genus QLdi" 

 chirus is one so extraordinary, that I am sure it will be noticed 

 whei-ever the description of a new species of it may be found, 

 be it by itself or amongst those of other Staphylinidjje. The 

 case would be different if the object of the description were a 

 Homalota or the like. 



PROCEEDINGS OF LEARNED SOCIETIES. 



, ROYAL SOCIETY. 



December 18, 1856. — The Lord Wrottesley, President, in the Chair. 



" On the Scelidothere {Scelidotherium leptocephalumy Owen), a 

 large extinct Terrestrial Sloth." By Professor R. Owen, F.R.S. 



The extinct species of large terrestrial Sloth, indicated by the 

 above name, was first made known by portions of its fossil skeleton 

 having been discovered by Charles Darwin, Esq., F.R.S., at Punta 

 Alta, Northern Patagonia. These portions were described by the 

 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 Ay res 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 



