104 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 56. 



TfflNOBADISTES, new genus. 



A new genus of ground sloths, most closely related to GnatJiopsis 

 Leidy Type, T, segnis, a new species described below. Based on an 

 astragalus, in the front half of the upper surface of which there is a 

 deep ligamentous fossa opening forward; the lower face also crossed 

 from front to rear by a ligamentous fossa. 



THINOBADISTES SEGNIS, new species. 



Plate 27, figs. 1, 2. 



Type specimen. An astragalus, No. 3335, of the U. S. National 

 Museum. 



Type locality. — WilUston, Florida. 



Type formation. — Pleistocene. 



Characters. — Those of the genus. 



In the United States National Museum there is a left astragalus of 

 a large ground sloth which is recorded as having been collected by 

 the United States Geological Survey in 1887, in Levy county, 

 Florida. The catalogue number is 3335, and the bone is recorded a 

 Mylodon Jiarlani. It seems probable that the collector of the speci- 

 men was Mr. J. B. Hatcher; and it is quite certain that it was found 

 at "Mixon's bone bed," near Williston, where many other fossils 

 have been secured. 



It appears that this bone had been studied by Doctor Leidy, for 

 there is writing on it in his chirography ; but he has not indicated on 

 it any generic or specific name. 



Supposing that the bone belonged to Mylodon liarlani, the astraga- 

 lus of which appears to be known only from Harlan's brief descrip- 

 tion and poor figure,* the writer first compared it with that of Mylodon 

 rohustus, as described and figured by Richard Owen.^ It soon be- 

 came evident that the Florida bone was quite different from the 

 correspondmg one of the South American species. On plate 27, 

 figures 1, 2, are presented two views of the bone from Florida. From 

 figure 1 it will be seen that there is on the upper face a deep fossa 

 extending from the front of the bone to its center. A large part of 

 this fossa is occupied by a rough surface for hgamentous attachment, 

 the apex of which is midway between the front end of the bone and 

 the hinder border of the articulation for the tioia. In all directions 

 away from the fossa just mentioned the surface for articulation with 

 the tibia is strongly convex. In Mylodon rohustus the corresponding 

 fossa is evidently much shorter and shallower, and the surface for 

 the tibia is much flatter and apparently even concave posteriorly. 

 The greatest differences are seen, however, on the lower surface of 



» Amer. Joum. Sci., vol. 44, 1843, p. 78, pi. 1, fig. 16. 



s Descr. skel. Mylodon rohustus, 1842, pp. 117, 131, pis. 21-23. 



