344 Mr. Owen's Letter to the Editors on 



notice in the Edentate fossil, in the Missonrian collection of Mr. 

 Koch ; but the Dr. having referred the lower jaw in the posses- 

 sion of Mr. Graves of New York, to the Megalonyx laqueatus, 

 failed to detect the specific identity of the broken lower jaws of 

 the Edentate animal in Mr. Koch's collection, with the New 

 York specimen ; and not having been aware that I had separated 

 Mr. Graves' fossil generically from the Megalonyx laqueatus, 

 Dr. Harlan, perceiving that the Missonrian Edentate fossils were 

 not referable to Megalonyx, conceives them to belong to an un- 

 described genus. 



I have carefully examined these Edentate remains, brought by 

 Mr. Koch from Benton County, Missouri. They belong to the 

 same species of Mylodon as the lower jaw in the possession 

 of Mr. Graves, in New York ; and the name Orycterotherium 

 Missouriense, must therefore sink into a synonym of Mylodon 

 Harlani. 



The humerus and tooth from the Oregon Territory, figured 

 and described by Dr. H. C. Perkins, in Vol. xlii, of your valua- 

 ble Journal, belong to the Mylodon Harlani.* 



In the best preserved portion of the lower jaw of this species, 

 in Mr. Koch's collection, there was evidence of four teeth, and 

 no more, on each side. The first tooth resembled that in the 

 Mylodon Darwinii, having a simple elliptical transverse section, 

 and being neither ribbed nor fluted. The empty socket in the 

 lower jaw at New York, erroneously referred by Dr. Harlan to 

 his Megalonyx laqueatus, indicates the tooth to have had a sim- 

 ilar simple form ; the remaining three teeth in that jaw are iden- 

 tical in configuration and size, with those of the so called Oryc- 

 terotherium. They resemble in structure the teeth of the Sloth 

 and Megatherium, and widely differ from those of the Oryctero- 

 pus. The humerus of the Missonrian Mylodon Harlani, like 

 that of the South American species of Mylodon, resembles the 

 humerus of the Megatherium and Bradypus tridaetylus in being 

 imperforate, whilst that of the Orycteropus is perforated at the 

 inner condyle. 



The ungual phalanges or claw-bones of the Missouri Mylodon, 

 retained more or less perfect traces of the osseous sheath con- 



* Mr. Owen of course had not seen Dr. Harlan's description and figures of the 

 Missouri fossil bones, (Orycterotherium Missouriense,) contained in this vo!ume ( 

 p. 69. The number containing that article was not published when Mr. Owen'a 

 letter was written. — Eds. 



